半干旱农牧交错区人工林退化:概化模型和现状评价

在干旱半干旱地区,造林通常被作为荒漠化防治最为有效的措施之一,然而这一区域人工林退化也是不可回避的事实。本文以半干旱农牧交错区的内蒙古伊金霍洛旗为例,对其林地退化状况进行评价。根据野外调查结果我们建立了一个林地退化概化模型,据此筛选出湿润指数、植被指数、土壤类型和土壤侵蚀模数4个评价指标,并采用GIS对该区人工林退化状况进行评价。结果表明,在336.09km2人工林中,退化面积达311.35km2,其中轻度、中度和重度退化面积分别为78.97,119.73和112.65km2。退化人工林的防治重点应放在现有林的改良和造林植物种特别是灌木种的选择上。图4参15。

Artificial woodland degradation in semi-arid agro-pastoral transitional area: conceptual model and status assessment

Planting trees was used as one of cost-effective measures for desertification control in arid and semi-arid areas of China. Wood- land 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-arid 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 km2 of total woodland area, 311.35 km2 woodland were under degradation, and the area for slight, medium, severe degradation was 78.97, 119.73 and 112.65 km2, 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.