引用本文:王伦江,张兴昌.苜蓿影响砒砂岩陡坡侵蚀的水动力学机理研究[J].土壤学报,2020,57(2):284-295. DOI:10.11766/trxb201901080603
WANG Lunjiang,ZHANG Xingchang.Hydraulic Mechanism of Alfalfa Controlling Soil Erosion on Steep Slopes of Pisha-sandstone[J].Acta Pedologica Sinica,2020,57(2):284-295. DOI:10.11766/trxb201901080603
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苜蓿影响砒砂岩陡坡侵蚀的水动力学机理研究
王伦江1,3,张兴昌1,2
1.西北农林科技大学水土保持研究所,陕西杨凌 712100;2.中国科学院水利部水土保持研究所黄土高原土壤侵蚀与旱地农业国家重点实验室,陕西杨凌 712100;3.北京师范大学地理科学学部,北京 100875
摘要:
砒砂岩陡坡是黄河中游泥沙和粗沙的重要来源地,草本植物恢复是防治土壤侵蚀的重要措施,然而对草本植物防治砒砂岩陡坡侵蚀机理的研究却较少。为明确草本植物防治砒砂岩陡坡土壤侵蚀的水动力学机理,通过小区径流冲刷实验,分析不同苜蓿密度(株间距为2 cm、4 cm、5.6 cm、8 cm)下砒砂岩陡坡产流产沙和径流水动力学特性变化。结果表明,苜蓿覆盖下砒砂岩陡坡产沙主要发生在径流冲刷前期,产沙过程呈单峰形式。产沙速率与径流流速和水流功率均呈幂函数形式关系,决定系数( R2)分别为0.94和0.68。苜蓿能减小砒砂岩陡坡径流量,影响径流水动力性质。株间距增大的过程中坡面径流阻力呈幂函数形式减小,导致径流流速和水流功率呈幂函数形式增大,苜蓿通过茎秆和根系影响径流水动力过程。细沟形成前,苜蓿主要通过茎秆的作用增大径流阻力;细沟形成后苜蓿还可能通过其出露于细沟中的根系影响股流的阻力状况。由于径流水动力性质和土壤抗冲性质的变化,砒砂岩陡坡侵蚀量大大减小,产沙量随苜蓿盖度增大呈幂函数形式减小( R2=0.55)。相比于盖度,苜蓿株间距与产沙的关系更为密切( R2=0.93),原因可能是株间距更能综合地反映苜蓿整体 (地上和地下部分) 防治砒砂岩陡坡侵蚀的作用。研究可以为砒砂岩陡边坡侵蚀防治中草本植物的配置提供一定的科学依据。
关键词:  砒砂岩  陡边坡  草本植物  盖度  株间距  水动力学特性
基金项目:中国科学院科技服务网络计划(KFJ-STS-ZDTP-12)和国家重点研发计划项目(2017YFC0504504)
Hydraulic Mechanism of Alfalfa Controlling Soil Erosion on Steep Slopes of Pisha-sandstone
WANG Lunjiang1, 3,ZHANG Xingchang1, 2
1. Institute of Soil and Water Conservation, Northwest A & F University,Yangling, Shaanxi 712100, China;2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Soil and Water Conservation,CAS&Ministry of Water Resources,Yangling, Shaanxi 712100, China;3. Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
Abstract:
Steep slopes of Pisha-sandstone are the major sources of silt and coarse sand in the mid-reaches of the Yellow River of China. Revegetation of herbaceous plants on the slopes is one of the most effective measures to control soil erosion thereupon. However, so far little has been reported in the literature about how herbaceous plants influence soil erosion on steep slopes of Pisha-sandstone. 【Objective】This study aimed to quantitatively study effects of herbs on soil erosion on steep slope of Pisha-sandstone and hydraulic mechanism of the erosion. 【Method】 A total of ten artificial slopes (37°) were set up and planted with alfalfa plants different in spacing (2 cm、4 cm、5.6 cm、8 cm ) in Erdos, Inner Mongolia. Plot runoff scouring experiments were carried out with a constant inflow (2 L.min-1). Runoff and sediment yields on the slopes and variation in hydraulic features of the runoff were monitored and analyzed to explore the mechanism of alfalfa controlling soil erosion. 【Result】 Results show sediment yield on the slopes planted with alfalfa occurred in the initial period of runoff and scouring period, forming a single peak. Sediment yielding rate increased with flow velocity and stream power in a power function, with determination coefficients being 0.94 and 0.68, respectively. The presence of alfalfa decreased runoff volume and changed the flow hydraulics. Flows on the alfalfa covered slopes were in a laminar and subcritical state. Increase in plant spacing resulted in greater flow velocity ( R2=0.90) and stream power ( R2=0.62), but a decrease in flow resistance ( R2=0.87). Stems and roots of alfalfa played an important role in altering flow hydraulics. Before rill formation, stems of the plants hindered the flow of runoff. However, after rill formation, apart from the stems, roots of the plants standing out in the rills inceased resistance to the flows therein. Due to the changes in flow hydraulics and soil erodibility, soil loss on the slopes decreased exponentially with alfalfa coverage ( R2=0.55). However, compared to the alfalfa coverage, plant spacing was more closely related to soil loss ( R2=0.93). 【Conclusion】 Plant spacing may reflect more comprehensively the effect of alalfa as a whole (shoots and roots) on controlling soil erosion of steep slopes of Pisha-sandstone. The study may provide a certain scientific basis for planting herbs on steep slopes of Pisha-sandstone for erosion control.
Key words:  Pisha-sandstone  Steep slope  Herbaceous plant  Coverage  Plant spacing  Hydraulics