稻田改为茶园后土壤铁形态与磁学性质演变特征

以四川省名山区稻田及由稻田改造的茶园土壤为研究对象,采用铁形态连续分级提取与环境磁学技术相结合的方法,分析铁氧化物与磁学特征随土壤利用方式及植茶时间变化而变化的特征。结果表明,稻田及不同植茶年限(3、6、10年)茶园土壤110cm土体均表现为可还原铁(Red-Fe)>可氧化态铁(Oxi-Fe)>酸溶态铁(Acid-Fe)；稻田改为茶园以及随着植茶年限延长,表层(0-10cm)及亚表层(10-20cm)土壤Acid-Fe、Oxi-Fe明显增加,而整个土体Red-Fe降低。稻田改为茶园3年后, 0~30cm土壤表现出质量磁化率(MS)、饱和等温剩磁(SIRM)、软剩磁(IRMs)升高,而硬剩磁(IRMh)降低；随着植茶年限的延长,土体总体表现出各磁性参数均降低的趋势,亚铁磁性矿物主导土壤磁性特征变化。稻田改为茶园后土壤逐渐酸化且有机质积累,使亚铁磁性矿物不稳定,进一步导致Red-Fe溶解并向Acid-Fe、Oxi-Fe转化,且随植茶年限的延长,部分铁氧化物结晶度会增加。

Evolution of Iron Morphology and Magnetism in Soil Converted from Paddy Field to Tea Garden

Taking the paddy field which be changed to tea garden soil in mingshan district of Sichuan Province as the research object, and the continuous extraction and environmental magnetic technology were used to analyze the changes of iron species and magnetic characteristics with soil utilization and tea planting time. The results show that the 110 cm soil mass with different tea planting years (0, 3, 6, 10 years) all are reducible iron (Red-Fe) > oxidizable iron (Oxi-Fe) > acid-soluble iron (Acid-Fe).The Acid-Fe and Oxi-Fe in the surface layer (0-10cm) and subsurface layer (10-20cm) of the soil increased significantly with the change of paddy field to tea planting and tea planting years, and Red-Fe decreases in the whole soil mass. Three years after the rice field was changed to tea garden, the soil mass magnetic susceptibility (MS), saturated isothermal remanence (SIRM), soft remanence (IRMs) increase and hard remanence (IRMh) decreases. However, with the extension of tea planting years, the magnetic parameters of the soil decreases, and ferromagnetic minerals dominates the change of soil magnetic characteristics. After the paddy field is replaced by tea planting, the soil is gradually acidified and organic matter accumulate, which make ferromagnetic minerals unstable, and further led to the transformation of Red-Fe into acid-Fe and Oxi-Fe. With the extension of tea planting years, the crystallinity of some iron oxides increases.