结果表明：城市土壤演变过程中土壤物理性质和养分含量发生了明显的变化。
The results showed: There were apparent changes of physical properties and nutrition content in the evolution process of city soil quality.
复活节岛上土壤中的一种微生物产生的化学物质在亿万年的演变中，本应与人类没有直接关系。
A tiny molecule harvested from a soil bacterium on Easter Island that evolved billions of years ago for no obvious purposes should have nothing to do with human beings.
因此，植被对土壤侵蚀和地貌演变，既有正的作用，也有负的作用。
Thus, influences of vegetation on soil erosion and geomorphic evolution can be positive or negative.
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