Abstract: In this research, the impact of Glycyrrhiza uralensis planting on soil quality was elucidated using principal component analysis on data from G. uralensis stands of different ages, to include a time dimension. It was found that: 1) After planting G. uralensis, soil average infiltration rate, total porosity, available N, available P, organic matter, enzyme activities (urease, phosphatase, polyphenol oxidase and dehydrogenase) and proportion of bacteria significantly increased, while soil bulk density, fungi number and its proportion markedly decreased and other indexes did not change significantly. 2) With increased G. uralensis stand age, significant increases in soil moisture content, pH, available N, organic matter, soil enzyme activities (urease, phosphatase, invertase and dehydrogenase), number of bacteria, number and proportion of actinomycete were observed, while available K and proportion of bacteria were markedly decreased. After establishment, available P initially increased but then decreased with age in older stands. Visibly obvious changes in soil average infiltration rate, field capacity, bulk density, total porosity and proportion of fungi were not quantified . Among soil microbial groups in G. uralensis stands, actinomycetes had the greatest comparative abundance, followed by bacteria and fungi. 3) A significant, positive correlation between number of bacterial and actinomycete was found, and also a similar relationship between those two groups and activities of urease, phosphatase and invertase. Negative correlation between fungi and bacteria, actinomycete, all enzymes were universally insignificant. Enzyme activities, besides polyphenol oxidase, were significantly and positively correlated with each other. 4) Soil quality of 3-year-old stands of G. uralensis was similar to that of fields of 4-year-old stands, and overall soil quality in fields of G. uralensis increased with stand age. Multivariate evaluation of results using principal component analysis showed that, in contrast to shifting sandy land, the soil quality of fields of 3-year-old and 4-year-old G. uralensis showed marked improvement.

Key words: Glycyrrhiza uralensis, soil quality assessment, planting years, principal component analysis