不同植茶年限土壤团聚体及其有机碳分布特征

作为土壤结构的基本单元和土壤肥力的重要组成部分,土壤团聚体对土壤的物理、化学和生物特性均有重要影响。试验选取了雅安市名山区中峰乡生态茶园区12—15a、20—22a、30—33a和50a的茶园,研究其土壤团聚体及其有机碳总量、储量和活性组分的分布特征,探究植茶年限对土壤团聚体及其有机碳分布的影响。结果表明:(1)研究区土壤以2 mm粒级团聚体为主,约为70%—80%,且在0—20 cm土层植茶20—22a土壤团聚体含量最高;(2)茶园土壤团聚体有机碳含量随团聚体粒级的减小而增加,最大值出现在0.25 mm粒级团聚体,且在植茶50a时达最高值,0—20 cm土层团聚体有机碳含量均高于20—40 cm,土壤团聚体水溶性有机碳和微生物生物量碳随植茶年限的延长呈先增加后降低的变化趋势,植茶30—33a时含量最高,且小粒级团聚体水溶性有机碳含量较高而微生物量碳较低;(3)土壤团聚体对有机碳的贡献率约有70%来自2 mm粒级团聚体,团聚体有机碳储量随植茶年限延长呈增加的趋势,不同植茶年限0—20 cm土层各粒级团聚体有机碳储量均高于20—40 cm土层,且以0.25 mm粒级团聚体有机碳储量最高。研究结果在一定程度上揭示了不同植茶年限土壤团聚体及其有机碳的分布特征,可为改善区域土壤质量及实施退耕还茶工程提供理论指导。

Distribution characteristics of soil aggregates and its organic carbon in different tea plantation age

Soil organic carbon (SOC) is a complicated composition, which could be influenced by many factors such as land use, soil management regimes, soil property and even climate. Understanding its dynamics can know which of the parts are active or passive due to either physical protection or biochemical resistance, or both. The labile fractions, such as water-soluble organic carbon (WSOC) and microbial biomass carbon (MBC), have a much shorter turnover time and thus have been suggested as an early indicator of the effects of either soil management or cropping systems on total organic carbon (TOC) quality. As an important component of soil structure and fertility, soil aggregates have huge effects on the physical, chemical and biological properties of soil. Investigating the formation and stabilization of soil aggregates is very necessary to understand dynamics of soil organic matter. Tea plantation age has great potential to affect soil aggregates and carbon pools. Therefore, knowledge about the different tea plantation ages effecting on soil aggregate and SOC distribution is essential for understanding the carbon pools changes of tea plantation ecosystem. Therefore, in the present study, we compared the distribution patterns of organic carbon within soil aggregates among four different plantation ages (12-15, 20-22, 30-33 and > 50 years old) located in Zhongfeng Township of Mingshan County, Sichuan. The results showed that:(1) The greatest proportion of aggregates was observed at the size of > 2 mm in each tea plantation which approximately accounted for 70-80% of all aggregates. SOC contents of aggregate fractions in the 0-20 cm soil layer were the highest in the tea plantation of 20-22 years old. (2) SOC contents of aggregate fractions increased gradually with decreasing particle size, and the maximum values of SOC contents were found in the aggregate fractions of < 0.25 mm diameter in tea plantations of > 50 years old. SOC contents of aggregate fractions in the 0-20 cm soil layer were higher than those of 20-40 cm soil layer. The contents of WSOC and MBC in the aggregate fractions decreased after an increase along with rising ages of the tea plantations. The maximum values of the contents of WSOC and MBC in the aggregate fractions were found in the tea plantation of 30-33 years old. The contents of WSOC in the smaller size aggregates were higher and the contents of MBC in the smaller size aggregates were lower. (3) 70% of organic carbon resulted from the aggregate at size of > 2 mm. SOC storage presented an increasing trend in different soil layers aggregates of all particle sizes along with rising age of the tea plantations. SOC storage of aggregate fractions in the 0-20 cm soil were higher than those of 20-40 cm soil layer, and the maximum values of SOC storage in the aggregate fractions were observed at size of < 0.25 mm diameter. The results partly explored the distribution characteristics of SOC of aggregates in different tea plantation ages, and it would provide theoretical guidance for returning farmland to tea and improvement of soil quality in the study area.