基于沙地植被指数的荒漠化评价方法

混合像元是影响基于遥感技术的荒漠化评价精度的主要原因。本研究通过光谱混合分析技术进行了亚像元尺度上荒漠化信息提取,并在深入研究荒漠化评价指标的基础上,利用所提取的农田信息与沙生植被信息构建了用于荒漠化评价的沙地植被指数,并与常用植被归一化指数进行比较。结果表明,沙地植被指数对荒漠化地区植被探测能力明显优于植被归一化指数,更适合于区分不同程度的荒漠化土地。对毛乌素沙地评价结果表明,毛乌素沙地荒漠化十分严重。     

走出治沙与退耕中的误区

近半个世纪沙漠化防治的结果是局部改善,整体恶化和治理赶不上破坏,本文分析提出了林草(灌)等四个误区和走出误区的三条建议,以及将发展生产与修复生态在源头上结合可收到生态生产共建双赢之效的观点。     

Land-use change and climate

Human activities in Australia and world-wide cause, or contribute to, desertification, deforestation, salinization and soil erosion, and also to reforestation, irrigation and landscape ‘management’. Human-induced land-use changes impact on the Earth's climate both locally and on a larger scale, right up to disturbance of the general circulation and hence the global climate. People have become a major environmental agent acting on the future climate through land-use change, particularly deforestation (and reforestation), desertification (which often includes overgrazing and excessive exploitation of vegetation), agricultural expansion, and soil erosion and degradation. The largest impact of land-use change on the future climate seems likely to be as a result of enhanced greenhouse gas emissions. At the same time, rapidly increasing populations, especially in the tropics, demand additional food, water for drinking and cleaning, and materials for the construction of shelters—all of which depend upon sustaining a reasonable climate. Climate and human land-use requirements are linked, but the closeness of that link varies from intimate dependency to callous disdain. In this paper, the impacts of human-induced land-use changes on future climate are explored in the context of the projections of global climate models.     

宁夏盐池县防沙治沙区土壤粒度、SOC及TN的空间异质性

为了探究宁夏盐池县实施防沙治沙措施后风沙土粒度特征变化对其防沙治沙区生态环境恢复的指示作用,以该区王乐井乡作为研究对象,通过野外采样及室内试验,分析了沙漠化治理区土壤粒度、土壤有机碳(SOC)及土壤全氮(TN)的空间分异特征及其相关性.结果表明:该区域风沙土优势粒级是细沙,各粒级均表现为中等变异,中沙和粉沙体积分数较低...     

Estimated Holocene soil carbon-soil degradation in Nevada and Western Utah, USA

There is much interest in predicting future carbon-soil degradation and that occurring today. We have National Soil Survey Laboratory data to assess some of the soil carbon degradation in the Great Basin and western Utah. For this we included data on 32 Nevada and Utah soils on Pleistocene geomorphic surfaces at elevations of 973 to 3172 m. Their mean annual precipitation (MAP) ranges from 20 to 55 cm and mean annual soil temperatures (MAST) from 5 to 12 °C. The MAP and MAST closely correlate with elevation (E) (r = 0.96 and − 0.97 respectively). Mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle) dominates vegetation at the higher, colder elevations. Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) and juniper (Juniperus L.) dominate at intermediate elevations. Little sagebrush (Artemisia arbuscula Nutt.) and related desert species dominate at the lower, warmer elevations. We used acid dichromate digestion and FeSO₄ titration to analyze for soil organic carbon (SOC) and bulk density and coarse fragments in the soils to put the data on a volume basis. The soils are well drained and uncultivated. Accumulation of organic carbon in each pedon (OCp) is correlated to MAP and MAST (r = 0.81, and − 0.78 respectively). We predicted OCp from the relationship,

(1)

r² = 0.64, S.E. = 1.30, n = 32. The soil OC degradation that may have occurred through the Holocene ranges from 35% at sites of the present Aridisols and Vertisols to 22% for the sites of the Mollisols and Alfisols. Eq. (1) shows that today, MAST rises of 1 to 3 °C would produce further OCp degradation from today's levels of 1% to 13% in Aridisols and Vertisols and 12% to 25% in the Mollisols and Alfisols respectively. It also shows that if the MAST drop of 6 °C predicted for the Pleistocene occurred, many of the Aridisols and Vertisols likely would have been Mollisols or Alfisols during the Pleistocene. A temperature rise of 1 °C in a century would likely move the Mollisol–Aridisol boundary from its present 2300 m elevation to an elevation of about 2900 m. A temperature rise of 3 °C in a century would likely move the Mollisol–Aridisol boundary from its present 2300 m elevation to elevations of the highest elevations in Nevada and to the middle of Idaho. Increasing the temperature by 3 °C will likely also increase the area affected by severe desertification in the southern Great Basin north by about 20%.     

Effects of desertification on soil organic C and N content in sandy farmland and grassland of Inner Mongolia

Desertification is one of the most serious types of land degradation. A field experiment was conducted during 2002 and 2003 in Horqin Sand Land, China to investigate changes in soil C and N contents in relation to land desertification. Four primary results were derived from this work. First, land desertification characterized by wind erosion resulted in a significant decrease in soil fine particles (clay + silt) with a corresponding increase in sand content. In comparison to non-desertified land, soil fine particle content decreased by up to 89.2%, and sand content increased by up to 47.2%, in the severely desertified land. Second, the organic C and total N in soil were mainly associated with the soil fine particles, and decreased significantly with desertification development. Organic C decreased by 29.2% and total N by 31.5% in the severely desertified land compared to the non-desertified land. Third, the decrease in organic C and N content was greater in desertified grassland than in desertified farmland. Fourth, the changes in organic C and total N content had a significant positive correlation with the soil fine particle content (P < 0.01) and a significant negative correlation with coarse sand content (P < 0.01), indicating that land desertification by wind erosion is mediated through a loss of soil fine particles, with a resultant decrease in soil organic C and total N.     

贵州喀斯特石漠化治理与生态文明建设

石漠化治理是我国当前最大的生态建设项目之一,也是喀斯特生态重建历史的机遇期。回顾和总结了过去20年石漠化治理存在的重要问题,提出贵州石漠化治理工程应定位为"生态贵州、和谐贵州、绿色经济"这一主题,石漠化治理的实质就是"生态文明",并指出走生态文明之路必须发展绿色经济,然后指出了今后重点要优先发展的方向。该研究为推动贵州的生态文明建设提供了参考。     

科尔沁沙地近50年动态变化与气候背景分析

根据奈曼旗1961-2010年土地沙漠化面积变化资料与奈曼气象站的气象资料,分析了科尔沁沙地最典型地区50年气候变化特征。     

锡林郭勒盟荒漠化状况的时空变化规律分析

以1981～2007年归一化差异植被指数(NDVI)数据为基础,在Arcgis软件的支持下,通过图形代数等方法,以植被指数的数值消长规律来表征锡林郭勒盟荒漠化的分布状况及时空变化规律。结果表明8,09、0年代,锡林郭勒盟无荒漠化的土地面积占17%～19%左右,无荒漠化与轻度荒漠化的土地面积共占50%以上,中度荒漠化的土地面积约占总面积的10%～12%,而重度和严重荒漠化的土地面积仅占总面积的32%左右;21世纪初期,锡林郭勒盟平均荒漠化状况出现了明显加重的趋势,无荒漠化土地面积占总面积的比例下降到不足6%,无荒漠化和轻度荒漠化的土地面积下降到总面积的32%左右,比809、0年代减少了20%以上,而重度荒漠化和严重荒漠化土地面积占总面积的比例迅速增加到近50%。因此,必须加强锡林郭勒盟草原区的生态保护与受损生态系统的恢复重建工作。     

辽蒙边界阻沙林带防沙治沙的作用浅析

辽宁省现有沙化、荒漠化土地面积为68.72万hm2。全部分布在朝阳、建平、北票、凌源、喀左、龙城等7县、市(区)的99个乡镇,其中北票、建平、朝阳县为重中之重。