关键词: 稻田, 茶园, pH, 腐殖质, 垂直分布

Abstract: In order to investigate the vertical distribution characteristics of soil pH and humus fractions in bleached paddy soil under 2 land use types， i.e. tea garden and paddy field， the pH， and the content of total humus carbon （CT） and its fractions in each soil layer were studied by sampling method of equal interval. The results were as follows: （1） Both paddy field and tea garden soil showed acid to strong acid reaction. However， after tea plantation， the acidification of bleached paddy soil increased; （2） On the whole， the vertical distribution characteristics about the content of CT and its fractions under both paddy field and tea garden appeared descend trend from surface layer to bottom layer. Meanwhile， the profile distribution characteristics of CT and its fractions were closely related to root distribution depth. The content of CT and its fractions below 30 cm soil layer under paddy field declined significantly. However， within 0—60 cm range under tea garden， it declined slowly; （3） The transformation from paddy field into tea garden favored the formation and accumulation of total humus carbon（CT） and fulvic acid carbon （CFA）. On the other hand， the content of humic acid carbon （CHA） and humin carbon （CHM） varied within different soil layers， as they were only accumulated in 40—60 cm soil layer other than in 0—30 cm soil layer; （4） The value of CFA/CT and CHA+FA/CT in each soil layer of tea garden was higher than that in paddy field， but the CHM/CT value was higher in paddy field than in tea garden. The value of CHA/CFA and CHA/CT varied within different soil layers. For instance， in 0—30 cm soil layer， it was higher in paddy field than that in tea garden. However， it was higher in tea garden than that in paddy field in 40—60 cm soil layer; （5） When the pH value was lower， the content of total carbon and its fractions were higher， and vice versa.

Key words: paddy field, tea garden, pH, humus, vertical distribution