选择pH、有机质、全N、碱解N等土壤理化因子作为评价指标,采用主成分分析结合聚类分析的方法对广西杉木主产区第1,2代杉木幼林土壤肥力进行评价,结果表明:大量、中量元素含量是决定土壤肥力的关键因素;连栽杉木土壤肥力综合评价指数F值在-1.253~1.536间。3个主产区内F值为负值占绝大多数(55.6%)。聚类分析结果表明:广西杉木连栽土壤可分为8类,其中根际土为一类,肥力较高;桂中地区土壤(除根际土)和20~40cm的土壤可划分为一类,肥力最低;其它土壤大致归作一类。2代杉木幼林土壤肥力较1代略高,这可能是由于森林经营措施(如炼山、采伐方法等)带来的短期影响,因此采取培肥沃土的森林经营模式,有利于防止杉木连栽林地地力衰退。

In this paper,soil pH value,the organic matter,total nitrogen,and available nitrogen (fifteen indexes) were chosen as evaluation indexes in principal component analysis in order to provide data supports for sustainable forest management of the continuous planting of Chinese fir in Guangxi,and offer the references to the soil fertility quality assessment of forest ecosystems of other regions.Soil fertility quality between the first and second generations of the young Chinese fir plantations were further assessed with principal component analysis and clustering analysis methods.The results were showed as following:macronutrient contents and secondary element contents were the pivotal factors for the soil fertility quality in the study area with comprehensive scores from -1.253 to 1.536.Among three Chinese fir producing areas,negative values occupied most.Soil fertility status of continuous planting of the young Chinese fir plantations could be divided into eight ranks by clustering analysis,that each root soil was divided into a separate rank,in which soil fertility was higher.Soil in the region of Guangxi(except for the root soil) and 20～40cm soil could be classified into a category,in which soil fertility was lowest.Other soils could be classified into a category,consequently plenty of organic and compound fertilizer are uesd for the fields of low soil fertility.The Soil fertility quality of the second generation of the young Chinese fir plantations was slightly higher the first one,it may be a temporary effect because of the forest management measures,for example,burning and cutting ways.Therefore,the forest managenments to fertilize the soil was proposed for prevention of land capability degradation.