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利用主成分分析法，对甘肃省三北地区的６９个县（市、区）三北二期工程建设效果进行多指标综合分析评价。计算结果表明，对主成分值影响权重较大的指标主要有现有森林覆被率、二期新增森林覆被率、防护林占地比率、零星植树株数、林业产值比重等。综合排序结果较好地反映了各县（区）三北二期工程建设效果的大小和差异，而且基本上符合全省林业生产建设实际状况
Using principal component analysis, the author made a multi-index comprehensive analysis and appraisal on the construction effect of the Three North Phase II projects of 69 counties (cities, districts) in the Three North regions of Gansu Province. The calculation results show that the main indexes that have a great influence on the principal component values are the existing forest cover rate, the second newly increased forest cover rate, the shelter cover ratio, the number of sporadic tree planting and the proportion of forestry output value. The results of the comprehensive ranking better reflect the magnitude and difference of the effect of the construction of the Three Northern and Northern Phase II projects in all counties (districts), and are basically in line with the actual conditions of the province’s forestry production and construction