为了评估不同天然植被群落类型的防风效应,我们在库布齐沙漠与黄河河岸之间的生态过渡带选取了柠条(C arag ana interm ed ia)、白刺(N itraria tangutorum)、拂子茅(C a lam ag rostis ep ig ejos)、赖草(L eym us seca linus)和芨芨草(A chna therum sp lend ens)等5种常见的天然灌草植被群落以及裸露沙地,并对其防风效应作了比较。结果表明,这几种不同天然植被群落类型的在近地面(10 cm)防风效应从大到小的次序是:赖草群落>芨芨草群落>拂子茅群落>裸露沙地>白刺群落>柠条群落;同一天然植被群落类型不同高度的防风效应也有较大差异;随距离地面高度的变化,不同植被群落风速降低率亦有变化。为干旱、半干旱地区天然植被群落的保护提供了科学依据。
Planting trees was used as one of cost-effective measures for desertification control in add and semi-add areas of China. Woodland degradation, however, is becoming an inevitable issue in these areas. In this paper, a typical county, Ejin Holo County, Inner Mongolia, China was selected for its assessment of artificial woodland degradation. A conceptual model for woodland degradation was delineated qualitatively based on field sampling survey, and four model-based indicators as humidity index （HI）, vegetation index （NDVI）, soil type （ST） and soil erosion modulus （EM） were screened out and used to a GIS-based method for artificial woodland degradation assessment in this semi-add agro-pastoral transitional area. All the indicator layers were overlaid and desertification assessed using simplified equation with equal weights for each indicators. The assessment results showed that in 336. 09 km^2 of total woodland area, 311.35 km^2 woodland were under degradation, and the area for slight, medium, severe degradation was 78.97, 119.73 and 112.65 km^2, respectively. It was suggested that much attention should be paid on woodland improvement and plant species selection, especially shrub species, before revegetation in similar areas.
Desertification is one of serious problems menacing the global environment and food security, andthe determination of causes of desertification is the basic issue for the coordinate actions to fight against it. InChina, the most serious desertification occurs in agro-pastoral transition zone. Considering the consistencyof socio-economic factors, Ejin Holo county in Inner Mongolia was selected out to analyze the desertificationcauses in this paper. Results showed that erratically climatic factors provided fragile background and drivingforces for desertification processes, and sand-covered surface and its underlying materials and specificgeomorphologic features have a great contribution to desertification processes as well. Socio-economicdevelopment, especially the traditional land management, the landuse patterns and the increase of livestockand human population were the root causes for desertification occurrence and expansion.
运用L ev ins生态宽度指数及P ianka生态位重叠指数对宁夏盐池荒漠草原人工封育区2002年及2003年生态位宽度及生态位重叠进行计量。结果表明:2002年封育区茵陈蒿、狗尾草生态位宽度值最大,分别为0.758、0.505,是2002年封育区的优势种;2003年封育区的优势种是茵陈蒿、狗尾草、老瓜头、苦豆子,其生态位宽度值分别为0.868,0.567,0.563,0.552。最大生态位重叠值2002年与2003年均未出现在优势种之间,2002年出现在赖草与叉枝鸦葱、新疆猪毛菜与志远之间;2003年出现在沙珍棘豆与中亚虫实、沙珍棘豆与狭叶米口袋、中亚虫实与狭叶米口袋之间。
