甘家湖荒漠林区生态恢复工程的影响因素及其环境效益评价

主要从生态恢复方面对甘家湖荒漠林区的恢复措施及其所产生的环境效益、社会效益及综合效应进行论证，分析甘家湖荒漠林区目前的状况及采取恢复措施后所能达到的效果。     

综合治理沙漠化灾害

本文对我国沙漠化灾害有自然和人为的两方面原因，进行了具体的分析和介绍。     

模拟氮沉降对内蒙古克氏针茅草原N2O排放的影响

随着工农业和社会的快速发展,我国成为全世界氮沉降最高的国家之一,温带草原地区的氮沉降水平局部可能超过3g·(m~2·a)~(-1).为研究氮沉降对我国典型草原生态系统氮循环的影响,在内蒙古太仆寺旗的克氏针茅草原,对土壤氧化亚氮(N_2O)的排放进行了为期1 a测定;同时,对该天然草地施加Na NO_3~-N以模拟氮沉降增加,进行了6个水平:CK(对照)、N_2[2g·(m~2·a)~(-1)]、N5[5 g·(m~2·a)~(-1)]、N10[10 g·(m~2·a)~(-1)]、N_25[25 g·(m~2·a)~(-1)]和N50[50 g·(m~2·a)~(-1)]的野外控制实验.结果表明,在自然氮沉降条件下,该生态系统N_2O的排放主要取决于土壤含水量和土壤温度,通过参数拟合估计全年N_2O-N排放量为0.10 g·(m~2·a)~(-1),约为当地氮沉降量的3%.而提高氮沉降可以显著提高N_2O的排放,特别是在高氮处理下(N_25和N50),N_2O的年排放量与模拟氮沉降量呈线性关系.我国温带典型草原较高的温室气体N_2O排放值得关注.     

从地气耦合角度讨论沙漠的成因

沙漠的成因是干燥气候和强大风力的产物.中国的大沙漠多在地壳运动相对稳定的地区,如塔里木地区、准噶尔地区、阿拉善地区、鄂尔多斯地区以及内蒙古东部地区等,因此可以认为,可能还有地下因素参与了沙漠的形成.其形成机制可能是:地壳运动稳定地区地下的携热水汽或其他携带热量的气体不易逸出,这样就不易在稳定地区大气中造成低气压状态,因而不易吸引冷热气团来交会降雨以及不易形成水汽的垂直对流降雨,这些后果叠加在更大范围的气候干燥背景上,使这些地区更加干旱,于是形成大沙漠.这种沙漠的扩展又在一些原来不是沙漠的农业区形成沙漠或沙地.     

不同干扰类型对呼伦贝尔草甸草原群落结构及物种多样性影响的比较

采用样方法,对比研究了2009—2011年刈割和围封干扰对呼伦贝尔草甸草原植物群落结构和物种多样性的影响. 结果表明:2009—2011年,围封干扰下建群种种群相对重要值分别为15.67%、17.73%、17.60%;而刈割干扰下建群种种群相对重要值分别为16.86%、14.84%、12.36%,呈明显下降趋势;表明围封干扰可促进建群种种群生长,而刈割则有一定的抑制作用. 2种干扰类型导致的植物群落生态类型变化趋势差异尚不显著. 2009—2011年,刈割干扰下,Margalef物种丰富度指数分别为6.05、4.58、4.27,Shannon-Wiener多样性指数分别为3.13、2.89、2.79,Pielou均匀度指数分别为0.90、0.91、0.90;围封干扰下,Margalef物种丰富度指数分别为6.46、6.03、5.32,Shannon-Wiener多样性指数分别为3.26、3.18、2.98,Pielou均匀度指数分别为0.87、0.87、0.85. 可见,在相同年份,刈割干扰下Margalef物种丰富度指数和Shannon-Wiener多样性指数均低于围封干扰,Pielou均匀度指数均高于围封干扰. 说明围封干扰有利于植物物种多样性的维持,而适度的刈割干扰则有利于植物群落的均一化.      

Past desertification processes of Minqin Oasis in arid China

Irrigated farming has affected most natural oases in western China since the Han Dynasty employed advanced agricultural techniques in dryland areas. To date, little is documented about the process through which these oases were modified by human systems. In this study, a multi-disciplinary approach incorporating analysis of historical documents, archaeological field surveys, satellite imagery, and GIS data was used to understand desertification processes in the Minqin Basin in Gansu Province, China, over the historical period. Results suggest that initial reclamation efforts around the Minqin Oasis were launched in the Han Dynasty (220–121 BC) and culminated in the Wei and Jin Dynasty (220–420). During the following 800 years from the Southern and Northern Dynasties (420–581) to the Yuan Dynasty (1271–1368), farmland disappeared and became desert when the region was taken over by nomadic people. The second period of intense development occurred in the Ming Dynasty (1368–1644) and was followed by another more aggressive development in the Qing Dynasty (1644–1911), which resulted in the largest reclaimed area in history. Oases were constantly reclaimed and subsequently abandoned and desertified over the whole historical period. The causes were complex, but the major cause was related to dynastic transition that often resulted in changes in national policies.     

沙漠地区沙尘气溶胶含量变化的原因分析

利用中国大陆气溶胶指数(TOMS AI)、太阳辐射、沙尘能见度、降水量等观测资料,对中国西北部沙漠地区沙尘气溶胶含量进行分析.结果表明,沙漠地区AI值不但取决于沙尘暴的发生,而且取决于太阳辐射.这表明沙尘暴起沙模型和尘卷风与干热对流的联合起沙模型互为补充,沙漠地区上空的沙尘气溶胶含量是它们共同作用的结果,而由太阳辐射引发的尘卷风与干热对流较沙尘暴过程更为重要.     

荒漠能源植物气化发电的环境影响评价

对荒漠生物质气化发电进行LCA评价,建立评价模型,在评价过程中选用了燃煤发电系统为参照.研究结果表明,生物质利用过程没有CO2的排放,整个发电周期中仅原料的生产、运输以及预处理过程消耗能量导致CO2排放,因此生物质气化发电方案的排放量远远小于燃煤方案,减排量达到了87%-94%.生物质发电与燃煤发电相比,对环境污染降低程度的总指数为3.68.生物质能源的开发大大削减了化石能源利用带来的环境污染问题,同时也能够缓解能源危机.     

荒漠化对新疆绿洲生态环境的危害

新疆荒漠化土地面积大,分布范围广,发展程度高,危害严重.目前,新疆的荒漠化面积为104.4×104km2,占全区总面积的65.25%.在自然因素和人为因素叠加影响下,新疆的荒漠化越来越严重威胁到绿洲生态环境.近几十年来,新疆过度开垦和人口增长过快已经给原本脆弱的生态环境带来巨大压力,加剧了水资源的耗用和土地荒漠化的进程.因此,防治荒漠化,是实现荒漠地区人口,资源与环境协调发展的根本途径.本文简要论述新疆日趋严重的荒漠化对绿洲生态环境的危害.并提出防治对策和见解.     

Association between plant species diversity and edaphic factors in the lower reaches of the Heihe River,northwestern China

The lower reaches of the Heihe River, in northwestern China, is characterised by unique local edaphic conditions that have influenced the development of local desert riparian forests. This study examines the variations in spatial variation patterns to reveal the relationships between plant species diversity and soil moisture/salinity/texture gradients at different soil depths, providing insights into the management and restoration of vegetation in ecosystems in the study area. The species–environmental relationships are investigated by redundancy analysis based on the plant species diversity matrix and the edaphic gradient matrix. A survey of 61 sampling plots identified 37 plant species in the study area. The distribution pattern of the plant species diversity are mainly affected by soil moisture, soil salinity, and soil texture at different soil depths. These edaphic factors are able to explain 98.47% of the total variation in the analysed vegetation dataset. Soil moisture, salinity, and texture content vary in terms of both the soil depths and the vegetation types in the study area. The plant community Class IV, xeric shrub, has the lowest soil water content among different vegetation types. The surface soil salinity differs for different plants and follows the order: Sophora alopecurides?>?Tamarix chinensis?>?Populus euphratica.