中文摘要：

桉树取代马尾松造林是我国南方典型土地利用变化类型之一，为了探讨该土地利用变化对土壤质量的影响，采用成对设计方法，研究了我国广西桉树取代马尾松造林对土壤养分、微生物生物量和酶活性的影响。结果表明：桉树取代马尾松造林后，土壤全碳、易分解碳库、中等易分解碳库、难分解碳库、全氮和碱解氮含量显著降低，但速效磷显著增加，这可能是由于桉树林施肥和磷素在土壤中移动性弱导致；土壤微生物生物量碳、氮、酚氧化酶、过氧化物酶、蛋白酶、脲酶和酸性磷酸酶活性显著降低。树种变化、桉树林轮伐期短、林下植被差、炼山、翻耕等可能是土壤养分、微生物和酶活性降低的驱动因子；施肥有助于缓解土壤养分降低。在林地转变和经营时，适当保持林下植被和凋落物、减少土壤扰动和合理施肥将有助于改善土壤质量，实现桉树林的可持续经营。

英文摘要：

Eucalyptus is an important tree species for afforestation in tropical or subtropical regions and many countries around the world have used it in afforestation. In South China, millions of hectares of local forests have been converted into Eucalyptus plantations. However, due to soil nutrient limitation in many areas and a high demand of Eucalyptus for nutrients, this kind of change in land use may exhaust soil nutrients and lead to deterioration of the soil in quality. In order to explore impacts of the practice on soil quality, soil samples were collected from 9 pairs of Eucalyptus and Pinus plantations in Guangxi, China, for analysis of soil nutrients, soil microbial biomass and soil enzyme activities and paired-t test. Pearson correlation analysis was done to explore relationships between soil nutrients, soil microbial biomass and enzyme activities. Results show that the replacement significantly decreased soil total carbon, labile carbon pool （I） and （II） , recalcitrant carbon pool, total nitrogen and alkalytic nitrogen, but significantly increased soil available phosphorus, which might be a result of fertilization in the Eucalyptus plantations low in phosphorus mobility in the soil. The replacement also significantly decreased soil microbial biomass carbon and nitrogen, and activities of phenol oxidase, peroxidase, protease, urease and acid phosphatase. The significantly lower soil carbon, nitrogen, microbial biomass and enzyme activities suggested that conversion of Pinus plantations to Eucalyptus ones significantly decreased soil quality. Correlation analysis shows that （ 1 ） soil total carbon and nitrogen were positively related with soil microbial biomass carbon, microbial biomass nitrogen, cellobiosidase, peroxidase, protease and urease activities, （2） soil carbon/nitrogen ratio was positively related with 13 -1, 4-glueosidase, cellobiosidase and peroxidase activities and （ 3 ） soil acid phosphatase activity was negatively related with total and available phosphorus and positively w