Remote sensing parameterization of the processes of energy and water cycle over desertification areas

In order to understand the processes of land surface-atmosphere interaction over de-sertification area, it is indispensable to utilize of satellite remote sensing. Two scenes of LandsatTM were used to produce a set of maps of surface reflectance, MSAVI, vegetation coverage, sur-face temperature, net radiation, soil heat flux, sensible heat flux and latent heat flux. Statisticalanalysis based on these maps revealed some quantitative significant land surface characteristics.Future developments of the method are also discussed.     

Development of land desertification in Bashang area in the past 20 years

Natural conditions in Bashang area are characterized by zonal transitions which are liable to be impacted by natural disasters and intensified human activities. The extremely fragile eco-environment is also liable to have desertification formed and developed. In the 18 years from 1978 to 1996, the desertified land area of Bashang within the scope of the map nearly doubled, a total increase of 2199.11 km2, averaging an increase of 122.17 km2 per year. Moreover, the seriously desertified area increases rapidly. Land desertification in Bashang is the combined result of natural factors and irrational human economic activities. Cultivated land expansion, population growth, and overgrazing aggrevate desertification development.     

一次火箭防雹效果的雷达回波分析

根据作业云块的雷达回波资料及作业云块和非作业云块雷达回波的对比观测资料，分析了一次火箭防雹作业效果。结果表明：使用WR－1B型火箭进行防雹，只要作业时机、部位准确、及时，作业剂量适宜，效果是明显的。     

Symbols, not data: rare trees and vegetation history in Mali

Historical analysis of botanical literature concerning the trees Gilletiodendron glandulosum and Guibourtia copallifera in Mali's Manding Plateau reveals that the dominant representation of these plants has helped to perpetuate colonial-era theories of vegetation history, African land management, and natural resource politics in West Africa. The French botanist Aubréville described these plants as proof of the theory of vegetation history that blamed poor land management by rural Africans for a steady and continuing destruction of vegetation from its presumed original forest climax. Although Aubréville's representation of these trees was justified within the 1930s scientific context he worked, subsequent researchers uncritically maintained his conclusions even though the changed scientific context in which they worked did not justify such representation. Subsequent ecological research also failed to substantiate Aubréville's representation of these trees, yet several influential modern botanical works have uncritically accepted colonial-era botanical literature founded on his ideas. Thus, modern botanical works have perpetuated a simplistic and inaccurate narrative of resource use under an appearance of objectivity. As a result, policy recommendations based on the modern botanical sources remain almost identical to colonial-era policies. Based on the similarity of colonial-era and modern portrayals of these trees, this paper argues that a regional discursive formation recently described by other authors may be expanded to include southern Mali, which carries negative implications for decentralization reform in Mali.     

吉林省西部土地沙化动态变化

The sandy land of the western part of Jilin Province is located in the ecotone of semi-humid and semi-arid area in the temperate zone of China. The sandy desertification has widely spread in the region because of the vulnerable natural conditions and the unreasonable human activity; as a result of this, the precious land resources and the economic development in the area have been seriously impacted. In this paper, the sandy land ecologic environment geographic information system is established based on the multi-spectral, multi-temporal Landsat TM images and field investigation. The comprehensive indexes of sandy desertification extent assessment which include vegetation degradation, wind erosion extent and soil depth are presented to classify the sandy land in western Jilin into three levels--slight, moderate and severe sandy desertification with the support of GIS platform. The results demonstrate that the sandy desertification has been partly controlled in the past twenty years, except some small sites. However, this doesn‘t necessarily mean that there is nothing for more concern. The two main causes of sandy desertification have not been eliminated yet, one is its natural factor, especially the physical and chemical characters of sandy soil and dry climate; another is the immoderate economic activity of human being that has highly accelerated the sandy desertification process.     

我国西南岩溶地区土地石漠化研究

在西南地区分布着以贵州为中心的、面积约54万km^2的碳酸盐岩山区，它是我国喀斯特地貌最发育的地区。同时也是石漠化最严重的地区。石漠化的产生与发展既有自然方面的原因，又有人为方面的原因，究其根本原因，是其岩溶生态系统中土壤这个关键因子的脆弱性所致。文章试图从土壤这个角度来全新阐述石漠化的成因及防治对策     

元谋干热河谷土地荒漠化的人为影响

干热河谷是我国西南地区独特的生态类型，这里气候炎热，植被稀疏；生态环境脆弱，土地荒漠化比较严重．分析了人类活动对元谋干热河谷区土地荒漠化的影响．     

Desertification and animal biodiversity in the desert grasslands of North America

Studies of breeding birds and small mammals were conducted at a series of sites that form a gradient of severity of desertification. Desert grassland sites represented the least changed landscape units and mesquite coppice dunes represented the most severe degradation, an irreversibly degraded landscape unit. The hypothesis that desertification reduces species diversity was not supported by the data. Species richness and diversities (Shannon-Weaver H′) of breeding birds were higher in the desertified areas than in the grassland with one exception. Data from a site dominated by the exotic African grass,Eragrostis lehmanniana, in south-eastern Arizona showed that breeding bird diversity was lower at that site than at a site in the same region that was dominated by native grasses. Species richness, diversity (H′), and abundance of small mammals were also higher in desertified areas than in desert grassland. Most grassland species of birds and mammals persist in the desertified habitats and species that are characteristic of shrublands colonize desertified desert grasslands. This accounts for the increases in species richness. However some species such as the banner-tailed kangaroo rat,Dipodomys spectabilis, are eliminated when grassland degrades to mesquite coppice dune or eroded creosotebush communities. These data suggest that other measures of faunal biodiversity such askeystone speciesmay be better measures of the impact of desertification on animal biodiversity.     

农牧交错带典型地段土地沙化主要因素分析——以河北坝上张北县为例

本文应用灰色关联模型 ,对农牧交错带典型地段河北省坝上张北县土地沙化因素进行了分析 :发现影响土壤风蚀和土地沙化的主要自然因素是冬季平均气温和降水量 ,而并非年降水量和年平均气温。人类活动只是在气候变化的背景上 ,加速或减缓土壤风蚀和土地沙化过程。根据冬季平均气温和降水量的变化 ,人类可适当调整农业生产结构和生产方式 ,以减轻土壤风蚀和土地沙化 ,实现农业的可持续发展     

北京周边沙源区沙化土地光谱特征初探

针对我国土地沙化及 90年代以来环北京地区频繁发生的沙尘天气 ,以北京周边的河北省丰宁县、内蒙古多伦县及镶黄旗为研究区 ,用美国ASDFieldSpecTM FR全波段野外光谱仪对不同类型沙化土地进行了野外光谱测量 ;根据测量结果 ,对不同沙化土地的光谱特征及其响应机制进行了探讨 ,认为土壤湿度、草地类型、草群高度和盖度以及不同物候期植被光谱特征与沙化土地的平均光谱特征相关。应从区域植被和土壤的特征光谱段分析沙化土地的光谱特征