黄土高原吕梁山撂荒枣林土壤质量评价

Soil Quality Evaluation of Abandoned Date Palm Forest in Lüliang Mountain of Loess Plateau

为了探究枣林自然撂荒后土壤质量随年限的变化规律,为该区域土壤质量提升及生态发展提供理论依据,试验采用时空替代法,以山西吕梁山区坡地撂荒枣林土壤为研究对象,分析土壤物理、化学性质及酶活性在时间(清耕、撂荒2 a、撂荒6 a、撂荒14 a)和空间(0~5、5~10、10~20 cm土层)上的变化规律,并结合主成分分析与土壤质量综合指数来表征土壤环境恢复状况。结果表明,自然撂荒后,土壤紧实度随年限增加呈降低趋势,孔隙度增大。各撂荒年限有机质变化呈现先降低后增加的波浪式特点,撂荒6、14 a在0~5、10~20 cm土层增加较显著;有效磷、速效钾含量在土壤剖面上逐层降低的变化较为明显,撂荒14 a后速效钾含量在表层是清耕土壤的1.36倍。随撂荒年限增加,脲酶、蔗糖酶和碱性磷酸酶活性总体上表现为先减小后增加的趋势;对照清耕土壤,撂荒14 a土壤蔗糖酶和碱性磷酸酶活性在0~5 cm土层分别增加33.13%~117.62%和21.70%~56.13%。土地撂荒后,随着植被演替的进程土壤的质量指数总体逐渐升高。土壤质量综合指数从大到小依次为撂荒14 a(0.711)、撂荒6 a(0.548)、清耕(0.329)、撂荒2 a(0.119),表明撂荒后土壤质量在植被恢复过程中逐渐得到提高。在撂荒后土壤自我演替恢复中,随着土壤养分的回归、有机碳含量升高,土壤酶活性增强,促进土壤孔隙结构的形成,土壤质量得到改善。

To investigate the change law of soil quality with years after the natural abandonment of date palm forest,and to provide theoretical basis for the soil quality improvement and ecological development in the region,in this study,the spatiotemporal substitution method was used to analyze the changes of soil physical and chemical properties and enzyme activities in time(clear plowing;2 years,6 years,and 14 years of abandonment)and space(0-5,5-10,and 10-20 cm soil layers),combined with principal component analysis and soil quality composite index to characterize the soil environmental restoration status,using abandoned date palm forest soil on the slope of Lüliang mountain,Shanxi.The results showed that after natural abandonment,the compactness of the soil gradually decreased and the porosity increased with the extension of the abandonment years.The content of organic matter in different years of abandonment showed a wave-like characteristic of first decreasing and then increasing,and the increase was more significant in the 0-5 cm and 10-20 cm layers in 6 and 14 years of abandonment.The content of available phosphorus and available potassium decreased obviously on the soil profile with increasing soil depth and after 14 years of abandonment,available potassium content in the surface layer was 1.36 times of that in clear plowing soils.With the increase of the years of abandonment,urease,sucrase,and alkaline phosphatase activities generally showed a trend of first decreasing and then increasing.Compared with the clear plowing soils,the activities of sucrase and phosphatase increased 33.13%-117.62%and 21.70%-56.13%,respectively,in the 0-5 cm layer after 14 years of abandonment.After abandonment,the overall soil quality index gradually increased with the process of vegetation succession.The soil quality composite index was in the order from the highest to the lowest:14 years of abandonment(0.711)>6 years(0.548)>clear-cutting(0.329)>2 years(0.119),showing that the soil quality improved gradually after abandonment during the vegetation recovery process.During soil self-succession recovery after abandonment,with the return of nutrients and increase of soil organic carbon content,enzyme activity in soil was enhanced,promoting the formation of soil pore structure and improving soil quality.