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随着国家退耕还林还草战略的实施、植被覆盖的变化,林、草地植被恢复进程中土壤团聚体特征的变化受到广泛关注.本研究以黄土丘陵区西部的官山林场退耕后栽植的刺槐林地、撂荒草地为对象,选取退耕年限为10、25 a的林、草地,采用湿筛法测定各样地0~30 cm土壤的水稳性团聚体组成,比较退耕还林、还草和退耕年限(10、25 a)对土壤水稳性团聚体平均质量直径(MWD)和分形维数(D)的影响.结果表明:退耕10 a的林地0~30 cm土层水稳性大团聚体含量(R0.25)、MWD和D分别为57.60%、1.91 mm和2.73;退耕25 a的林地分别为60.17%、1.88 mm和2.74;退耕10 a的草地分别为59.89%、1.82 mm和2.74;退耕25 a的草地分别为72.69%、2.71 mm和2.61.进一步分析证明,随着退耕年限的增加,土壤团聚性增强;但林草地的变化存在差异:恢复10 a阶段,土壤团聚性林地尚优于草地,25 a后草地优于林地.各样地土壤的SOC含量与R0.25呈显著正相关关系(p<0.01),与D呈显著负相关关系(p<0.05).退耕类型和退耕年限对土壤团聚性有显著影响.
With the implementation of the national strategy of returning farmland to forest and grassland, the changes of vegetation cover, the changes of soil aggregate features during the process of forest and grassland vegetation restoration have received widespread attention.In this study, the changes of the characteristics of soil aggregate after returning farmland to Guanshan Forest Farm in the western Loess Hilly Forestland and abandoned grassland. The composition of water-stable aggregates in 0-30 cm soil of each site was determined by wet sieving method. Compared with returning farmland to forest, returning farmland and returning farmland Years (10,25 years) on average mass diameter (MWD) and fractal dimension (D) of soil water-stable aggregates.The results showed that the water-stable macroaggregates in 0-30 cm soil layer (R0.25), MWD and D were 57.60%, 1.91 mm and 2.73, respectively. The areas of 25 days after the conversion of cultivated land were 60.17%, 1.88 mm and 2.74 mm, respectively. The grassland ten days after returning farmland was 59.89%, 1.82 mm and 2.74, The grassland of returning farmland to 25 a was 72.69%, 2.71 mm and 2.61 respectively.Further analysis showed that with the increase of returning farmland, the soil aggregation increased, but there was a difference in the change of grassland and grassland: In the grassland, the grassland was better than the forest land after 25 years. (P <0.01), and had a significant negative correlation with D (p <0.05) .There was a significant negative correlation between the types of returning farmland and the returning farmland duration.