Distribution characteristics of microbial biomass carbon and nitrogen in soil aggregates under tea plantation | 茶园土壤团聚体中微生物量碳、氮的分布特征

Chinese. 目的弄清茶园土壤团聚体中微生物量碳、氮的分布特征，以期反映退耕还茶模式对土壤团聚体及其养分循环的影响，为协调区域土地利用及退耕还林（茶）工程的实施提供依据。方法采用野外调查和室内分析相结合的方法，以撂荒地和桉树人工林为对照，就茶园土壤团聚体中微生物量碳、氮的分布特征进行了研究。结果（1）茶园和对照撂荒地、桉树人工林土壤团聚体中有机碳含量基本随团聚体直径的减小而增加，最大值均集中于＜0.25 mm团聚体中；（2）茶园及对照地土壤微生物量碳、氮含量则基本随团聚体直径的减小而降低，其中茶园土壤团聚体中微生物量碳、氮含量最大值分布于5―2 mm团聚体中，茶园土壤除了＜0.25 mm团聚体外，其微生物量碳、氮的含量均高于撂荒地和桉树人工林同直径团聚体；（3）茶园及对照地土壤团聚体微生物熵基本随团聚体直径的减小而降低，其中茶园土壤团聚体微生物熵最大值分布于5―2 mm团聚体中，其分布规律与微生物量碳、氮基本一致。结论与撂荒地、桉树人工林相比，茶园土壤团聚体中微生物量碳、氮较为丰富，大团聚体中的含量尤为突出，表明退耕还茶是研究区一种较为理想的退耕模式。

English. Objective The distribution of microbial biomass carbon and microbial biomass nitrogen in soil aggregates of tea planted area was studied on purpose to reflect the influence of tea plantation on soil aggregates and its nutrient cycling, which can provide evidence for coordinating regional land use and returning farmland to forest/tea project. Method On the basis of field investigation and laboratory analysis, abandoned land and eucalyptus plantation were selected as contrasts, distribution features of microbial biomass carbon and microbial biomass nitrogen in soil aggregates under tea plantation were studied. Result The content of soil aggregates organic carbon comparatively increased as soil aggregates particles diameter reduced. The maximum soil aggregates concentrated with organic carbon were found at ＜0.25 mm diameter under tea plantation, abandoned land and eucalyptus plantation. The content of soil aggregates microbial biomass carbon, microbial biomass nitrogen comparatively decreased when soil aggregates particle diameter reduced under tea plantation, abandoned land and eucalyptus plantation. The maximum microbial biomass carbon, microbial biomass nitrogen was found in the soil aggregates of 2-5 mm diameter under tea plantation. Except ＜0.25 mm aggregates, the contents of soil aggregate microbial biomass carbon, microbial biomass nitrogen under tea plantation were higher than abandoned land and eucalyptus plantation within the same aggregates particle diameter. Soil aggregates microbial quotient generally decreased along with soil aggregates particles reduced under tea plantation, abandoned land and eucalyptus plantation. The maximum soil aggregates microbial quotient was mainly in the 2-5 mm aggregates under tea plantation, its distribution pattern was similar to microbial biomass carbon and nitrogen. ConclusionThe content of microbial biomass in tea plantation soil is more plentiful than in the contrast,especially for large aggregates,which shows that conversion of farmland to tea plantation is a relatively ideal model of set-aside patterns in study area.