松嫩平原北部未开垦黑土土壤物理性状垂直变化特征

Vertical Variation of Physical Properties of Uncultivated Black Soil in Northern Songnen Plain

[目的]探究松嫩平原北部未开垦黑土土壤物理性状特征,为黑土区退化土地恢复以及土壤质量评价提供重要的本底值参考。[方法]以未开垦黑土(天然次生林、五花草塘)为研究对象,测定0—140 cm土层范围土壤物理指标,运用主成分分析和聚类分析的方法,对土壤物理性状进行综合评价。[结果]未开垦黑土土壤容重随土层深度的增加逐渐增大,总孔隙度、毛管孔隙度、饱和持水量和毛管持水量则随土层深度的增加逐渐降低,且在0—60 cm土层范围内,天然次生林拥有更小的土壤容重以及更大的孔隙度和持水量;土壤质地在0—100 cm土层范围内为黏壤土,≥100 cm土层为粉质黏壤土;未开垦黑土水稳性团聚体含量、平均重量直径和几何平均直径均随土层深度增加呈先降低后增加趋势;整体上五花草塘0—10 cm土层土壤水稳性团聚体含量(WSA>0.25)、平均重量直径(MWD)和几何平均直径(GMD)分别比天然次生林高出37.14%,87.96%和110.52%,但在10—80 cm土层范围内天然次生林表现较高;天然次生林与五花草塘土壤团聚体分形维数(D)整体上差异不明显;通过主成分分析与聚类分析发现,未开垦黑土不同土层土壤物理性状综合表现存在明显差异,整体在0—10 cm土层内表现最优,且在0—40 cm土层范围内天然次生林土壤物理性状相对于五花草塘表现更优秀。[结论]松嫩平原北部未开垦黑土表层土壤物理性状明显优于深层土壤,且天然次生林与五花草塘土壤物理性状差异较大,天然次生林对于浅土层土壤物理性状拥有更好的改善效果。

[Objective]This study aims to investigate the physical properties of uncultivated black soil in the northern Songnen Plain,provide important background values for the restoration of degraded land and soil quality assessment in the black soil area.[Methods]The uncultivated black soil in the north of Songnen Plain,including natural secondary forest and tessellated meadow,was selected as the research object.Soil physical indexes were measured in the 0—140 cm soil layer,and the soil physical properties were comprehensively evaluated by using principal component analysis and cluster analysis.[Results]The soil bulk density of the uncultivated black soil increased gradually with the increase of soil depth,while the total porosity,capillary porosity,saturated water capacity,and capillary water capacity decreased gradually with the increase of soil depth.In the 0—60 cm soil layer,the natural secondary forest had smaller soil bulk density and larger soil porosity and water capacity.The soil texture was clay loam in the 0—100 cm soil layer,and silty clay loam in the≥100 cm soil layer.The water-stable aggregate content,mean weight diameter,and geometric mean diameter of uncultivated black soil all decreased first and then increased with the increase of soil depth.Overall,the soil water-stable aggregate content(WSA>0.25),mean weight diameter(MWD),and geometric mean diameter(GMD)in the 0—10 cm soil layer of the tessellated meadow were 37.14%,87.96%,and 110.52%higher than those of natural secondary forest,respectively,but the natural secondary forest showed better performance in the 10—80 cm soil layer.The fractal dimension(D)of soil aggregates was not significantly different between natural secondary forest and tessellated meadow.The results of principal component analysis and cluster analysis showed that there were significant differences in the comprehensive performance of soil physical properties in different soil layers of uncultivated black soil,with the overall performance being the best in the 0—10 cm soil layer,and the soil physical properties of natural secondary forest in the 0—40 cm soil layer being better than those of tessellated meadow.[Conclusion]The surface soil physical properties of uncultivated black soil in the northern Songnen Plain were better than the deep soil,and the natural secondary forest and tessellated meadow soil physical properties were significantly different.The natural secondary forest showed a better improvement effect on soil physical properties in the shallow soil layer.