植被恢复对黄土区煤矿排土场土壤团聚体特征的影响

目前关于植被恢复对排土场土壤团聚性的影响还不清楚,以植被恢复下黄土区露天煤矿排土场为研究对象,采用湿筛法测定了排土场土壤水稳性团聚体组成,研究了植被恢复类型(草地、灌木)和排土场地形(平台、边坡)对土壤团聚体特征的影响。结果表明:植被恢复促进了排土场水稳性团聚体的形成,平台0—20 cm土层水稳性大团聚体数量(R_(0.25))、平均重量直径(MWD)和几何平均直径(GMD)分别达到31.1%,0.70 mm和0.26 mm,边坡分别达到13.3%,0.37 mm和0.17 mm,均显著高于裸地,分形维数(D)在平台和边坡分别为2.91和2.96,均显著低于裸地;平台土壤团聚性要好于边坡,草地对于平台土壤团聚结构改良效果较好,而灌木对于边坡改良效果较好;排土场土壤有机碳和粘粒含量均与土壤团聚体指标有显著相关性。植被恢复提高了排土场土壤团聚性,植被恢复类型和地形对排土场土壤团聚体特征有显著影响。

Effects of vegetation restoration on soil aggregate characteristics of an opencast coal mine dump in the loess area

Soil aggregate structure is an important factor affecting soil fertility and erodibility. Reports have suggested that vegetation restoration may affect water-stable soil aggregates, but few studies have assessed vegetation restoration in the mining area on the Loess Plateau. This study was performed in the Heidaigou opencast coal mine dump of the Loess Plateau, which has been restored by vegetation reconstruction for 18 years. To study the effects of vegetation types and landforms on dump soil aggregate characteristics, we assessed three vegetation types (grassland, shrubland, and bare land) and two landforms (platform and slope) with 6 treatments and 126 samples. The water-stable soil aggregate composition was analyzed by wet sieving. The aggregates were separated into six size classes: >5 mm, 5-2 mm, 2-1 mm, 1-0.5 mm, 0.5-0.25 mm, and <0.25 mm. Macro-aggregate content (R_0.25), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D) were used as evaluation indexes. Soil particle size distribution was determined by an MS2000 laser granularity analyzer. Soil organic carbon (SOC) content was determined by potassium dichromate volumetry. Results showed that vegetation restoration promoted the formation of water-stable soil aggregates. The R_0.25, MWD, and GMD of the 0-20 cm soil layer were significantly higher in revegetated land than in bare land on both platforms and slopes. The R_0.25, MWD, GMD, and D in the 0-20 cm soil layer of revegetation land were 31.1%, 0.70 mm, 0.26 mm, and 2.91, respectively, on platforms, and 13.3%, 0.37 mm, 0.17 mm, and 2.96, respectively, on slopes. The soil aggregate quality on the plat form was better than on the slope. Artificial grassland had more significant improvement in soil aggregate quality than the shrubland on the platform of the dump, but the shrubland was better on the slope. The soil aggregate quality was lower in the surface layer than sub-surface layer on the platform. SOC content and soil clay content were significantly related to soil aggregate quality. Higher SOC content was noted with vegetation restoration on the platform than on the slope. The distribution of SOC content changed in the order grassland > shrubland > bare land on the platform, but in the order shrubland > grassland > bare land on the slope. The clay, slit, and sand contents, respectively, averaged 10.52%, 54%, and 35.48% on the platform and 7.68%, 42.82%, and 49.50% on the slope. Significant correlations were noted between SOC content and soil aggregate indexes aswellas between soil clay content and soil aggregate indexes. Correlation analysis showed that water-stable soil aggregate properties were positively correlated with SOC and soil clay. Further, soil clay promoted the formation of water-stable soil aggregates, while the high SOC increased the particle size of water-stable soil aggregates and changed their size distribution. Our results suggested that soil aggregate quality improved significantly after 18 years of vegetation restoration, and vegetation types and landforms had significant influences on soil aggregate properties in this mining area on the Loess Plateau. In addition, our results showed the positive effects of vegetation restoration on water stability and soil structure of an opencast coal mine dump on the Loess Plateau, which reduced soil erosion and improved soil quality in this region.