Principal Component Analysis of Soil Physical and Chemical Properties in Successive Eucalyptus Plantation

To analyze soil physical and chemical properties in successive Eucalyptus plantation,principal component analysis(PCA)is used by determining principal component factors of soil.Principal component factors in different Eucalyptus generations are compared to illustrate the change of soil fertility.Results show that principal components in 0—20 and 20—40 cm soil layers are basically the same in Eucalyptus plantation.The first principal component composed of soil physical properties and the composition of three soil nutrients(N,P,and K)is the most important factor to soil fertility in the plantation.Integrated soil fertility declines with the increase of crop-rotation generations,especially after the 3rd generation.Integrated soil fertility is significantly reduced,compared with 1st and 2nd generations.The result indicates that maintaining good soil aeration and water permeability of soil,as well as N,P,and nutrient contents,is very important for maintaining the sustained and healthy development of Eucalyptus plantation.