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黄土丘陵沟壑区生物结皮对土壤抗蚀性能的影响

Soil anti-erodibility influenced by biological crusts in Loess Hilly and Gully Region

    摘要
  • 摘要: 生物结皮是重要的近地表组成成分，可能显著影响坡面侵蚀过程。为了探明生物结皮对土壤抗蚀性能的影响，作者选择陕西省安塞区县南沟小流域人为扰动较小的2块退耕坡地，生物结皮的类型分别为苔藓结皮和混合结皮（藻结皮+苔藓结皮），以附近无生物结皮发育的玉米地为对照。按结皮盖度等级（0~20%、> 20%~40%、> 40%~60%、> 6% 0~80%和> 80%~100%）选择50 cm×50 cm样方，设置保留生物结皮层和去除生物结皮层2个处理，测定或计算土壤紧实度、黏结力、饱和导水率、团聚体稳定性（常水头滴定法和湿筛法）和土壤可蚀性K因子等6个土壤抗蚀性能指标，基于上述指标采用加权综合法生成一个综合性抗蚀指数CSAI，综合反映生物结皮对土壤抗蚀性能的影响。结果表明：1）苔藓结皮发育的土壤，其饱和导水率、团聚体稳定性和综合性抗蚀指数CSAI均大于混合结皮；2）去除生物结皮层后，土壤紧实度、黏结力、饱和导水率、团聚体稳定性和综合性抗蚀指数CSAI均显著减小，而K因子显著增大；3）随着生物结皮盖度的增大，土壤紧实度、黏结力、团聚体稳定性和综合性抗蚀指数CSAI呈增大趋势，而饱和导水率和土壤可蚀性K因子呈下降趋势；4）与对照相比，有结皮发育的样地综合抗蚀性指数CSAI有所增加。表明生物结皮的生长发育可以有效增强土壤抗蚀性能，且苔藓结皮效果优于混合结皮；随着结皮盖度的增加，土壤抗蚀性能增强。研究结果对探明生物结皮提升土壤抗蚀性能的机理，评价生物结皮的水土保持效益，具有重要的理论和实践意义。

     

    Abstract:
    Background As one of the important near soil surface components, biological soil crusts (BSCs) may significantly affect soil erosion processes.
    Methods Two abandoned slope farmlands with little human disturbance covered by two dominant biological crust types (moss crust and mixed crust which is mixed by algae and moss) were selected in Xiannangou small watershed of Ansai, Shannxi province to investigate the effects of biological crusts on soil anti-erodibility. One nearby cropland of corn was taken as the control. Soil samples were taken from 50 cm×50 cm quadrats with different crust coverages of 0-20%, > 20%-40%, > 40%-60%, > 60%-80% and > 80%-100%. Soil penetration resistance, cohesion, saturated hydraulic conductivity, aggregate stability (constant raindrop number method and wet sieving method), and soil erodibility K factor were measured or computed. A weighted integrating method was utilized to produce a comprehensive soil anti-erodibility index (CSAI) based on those above soil anti-erodibility indicators to reflect soil anti-erodibility comprehensively.
    Results 1) Saturated hydraulic conductivity, aggregate stability, and comprehensive soil anti-erodibility index of soils covered by moss were greater than those covered by mixed crusts. 2) After BSCs were removed, soil penetration resistance, cohesion, saturated hydraulic conductivity, aggregate stability and comprehensive soil anti-erodibility index decreased, while K factor increased. 3) Soil penetration resistance, cohesion, aggregate stability and comprehensive soil anti-erodibility index increased, while saturated hydraulic conductivity and K factor showed a decreasing trend with BSCs coverage. 4) Compared to the control, the comprehensive soil anti-erodibility index of soils covered by BSC increased ranging from 0.50 to 0.52.
    Conclusions BSCs could effectively increase soil anti-erodibility and moss functions well than mixed BSCs. Soil anti-erodibility enhanced with BSCs coverage. The results are significant to detect the mechanism of BSC promoting soil anti-erodibility, and to evaluate soil and water conservation benefits of BSCs.

     

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