川西稻田改为茶园后土壤pH和腐殖质组成剖面分布变化特征

为了探讨稻田及由稻田改造的茶园这2种土地利用方式下，土壤pH和腐殖质组成的剖面分布特征，按等间距采样法采集土样，分析各土层pH、腐殖质总碳及其组分含量。结果表明：（1）稻田和茶园土壤均呈酸性至强酸性反应，植茶加剧了土壤的酸化；（2）稻田和茶园土壤腐殖质总碳及其组分含量自上而下均呈递减趋势，且剖面分布特征与土地利用和植物根系分布密切相关，在稻田30 cm以下土层中显著降低，在茶园0-60 cm土层内缓慢降低；（3）稻田改为茶园，有利于土壤腐殖质总碳（CT）、腐殖酸碳（CHA+FA）和富里酸碳（CFA）的形成与积累，而胡敏酸碳（CHA）和胡敏素碳（CHM）含量因土层不同而有差异，在0-30 cm土层内不利于其积累，但在40-60 cm土层内表现出明显的积累特征；（4）各土层CFA/CT和CHA+FA/CT表现为茶园＞稻田，CHM/CT为稻田＞茶园；而CHA/CFA和CHA/CT因土层不同而有异，0-30 cm范围内表现为稻田＞茶园，而40-60 cm范围内表现为茶园＞稻田；（5）土壤pH越低，腐殖质总碳及其各组分含量越高；反之，腐殖质总碳及其各组分含量越高，pH越低。

Changes in vertical distribution characteristics of soil pH and humus fractions after paddy field switched to tea garden in west Sichuan Basin

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.