The composition and stability of soil aggregates are important indicators for measuring soil quality, which would be affected by land use changes. Taking wetlands with different returning years (2 and 15 years) in the Yellow River Delta as the research object, paddy fields and natural wetlands as control, we analyzed the changes in soil physicochemical properties and soil aggregate composition. The results showed that soil water content, total organic carbon, dissolved organic carbon and total phosphorus of the returning soil (0-40 cm) showed an overall increasing trend with returning period, while soil pH and bulk density was in adverse. There was no significant change in clay content, electrical conductivity, and total nitrogen content. The contents of macro-aggregates and micro-aggregates showed overall increasing and decreasing trend with returning period, respectively. The stability of aggregates in the topsoil (0-10 cm) increased with returning years. Geometric mean diameter and mean weight diameter increased by 8.9% and 40.4% in the 15th year of returning, respectively, while the mass proportion of >2.5 mm fraction decreased by 10.5%. There was no effect of returning on aggregates in subsoil (10-40 cm). Our results indicated that returning paddy field to wetland in the Yellow River Delta would play a positive role in improving soil structure and aggregate stability.
土壤团聚体组成及稳定性是衡量土壤质量的重要指标,土地利用方式的转变会对其产生不同程度的影响。本研究以黄河三角洲不同退耕年限土地(退耕2年和15年)为对象,以退耕前土地(稻田)和未开垦的自然湿地为对照,分析退耕前后土壤理化性质和土壤团聚体组成及稳定性的变化。结果表明: 稻田退耕后土壤(0～40 cm)含水量、总有机碳、溶解性有机碳和全磷整体上呈现随退耕年限延长而增加的趋势,而土壤pH和容重呈下降趋势,但黏粒含量、电导率和全氮含量无明显变化。随退耕年限延长,土壤大团聚体含量整体上呈增加趋势,而小团聚体含量呈减少趋势。表层土壤(0～10 cm)团聚体稳定性随退耕年限延长而增加,退耕15年后,团聚体几何平均直径和平均重量直径较退耕前增加了8.9%和40.4%,而>0.25 mm团聚体质量分数则减少了10.5%;退耕对下层土壤(10～40 cm)团聚体的影响不明显。综上,黄河三角洲退耕还湿对改善土壤结构、提升团聚体稳定性起到积极作用。.
Keywords: Yellow River Delta; aggregate stability; returning paddy field to wetland; soil aggregate; soil property.