三峡库区不同植被覆盖坡地的土壤优先流运动特征研究
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华中师范大学城市与环境科学学院

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国家自然科学基金项目(41771261, 41601215)和湖北省自然科学基金重点项目(2015CFA141)资助


Research on the Characteristics of Preferential Flow Movement Along Varied Hillslopes Covered with Different Vegetation in the Three Gorges Reservoir Area
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College of Urban and Enviromental Sciences, Central China Normal University

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Supported by the National Natural Science Foundation of China (Nos.41771261, 41601215) and Natural Science Foundation of Hubei Province (No.2015CFA141)

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    摘要:

    研究土壤优先流运动特征与植被覆盖、坡位及土壤结构的关系,既能丰富山坡水文学的研究内容,还能进一步揭示森林涵养水源、保持水土的机制。以三峡库首大老岭林区常绿林、林灌混合落叶林和弃耕草地覆盖的坡地为研究对象,运用染色示踪和图像处理的方法,定量分析了3种植被覆盖的坡面上、下坡位的优先流染色特征,阐明了植被覆盖和坡位对土壤优先流运动和坡面水分入渗特征的影响。结果表明:(1)各样地染色面积比(SAR)和染色路径数(SPN)均呈现浅层高、深层低的特征。不同植被覆盖下,0~60 cm土层的SAR表现为落叶林坡地(44.2%)>弃耕坡地(36.1%)>常绿林坡地(35.3%),SPN表现为落叶林坡地(43条)>常绿林坡地(19条)>弃耕坡地(15条)。不同坡位下,0~60 cm土层的SAR表现为上坡(41.5%)>下坡(35.6%),SPN表现为上坡(23条)<下坡(28条)。落叶林坡地土壤染色深度最大,60~110 cm深度土层仍有很多狭长的水流路径延伸,而其他样地较少出现;(2)各样地的染色路径宽度(SPW)以1~10 cm和>10 cm为主,二者之和占剖面总染色面积的84.2%。除弃耕地坡上位点缺少均质流与非均质指流外,其他样点0~30 cm土层以均质流和非均质指流为主,30 cm以下为不同类型大孔隙流的混合分布;(3)弃耕坡地的侧向流最为明显,染色剂延伸到染液喷洒区外50 cm处,常绿林地和落叶林地仅延伸至10~20 cm。植被覆盖类型与坡位的耦合作用影响了土壤理化性质,从而影响优先流路径的形成与水分的入渗过程。常绿林与落叶林的水源涵养能力强于弃耕坡地,耕作形成的犁底层限制了弃耕坡地的水分垂直入渗,增加了侧向入渗与地表径流的风险,需要通过破除犁底层或种植根系发达的乔灌木以增加降雨蓄存能力。

    Abstract:

    【Objective】Studying the effects of topographic position, vegetation cover, and soil property on the characteristics of preferential flow in mountainous areas can enrich research content of hillslope hydrology, and further reveal the mechanism of forestland in soil and water conservation.【Method】Dye tracing experiments using Brilliant blue solution combined with photographed images analysis were carried out in the Dalaoling forestland of the Three Gorges area to explore the transport features of preferential flow along with soil vertical profile and lateral section. Six hillslope sites were selected to conduct dye tracing experiments, including the upslope and downslope covered by evergreen forest (EG), secondary deciduous forest mixed with shrubs (SDFS), and deforested pasture (DP), respectively. Several parameters were analyzed to demonstrate stained feathers along with vertial profile or lateral hillslope, including stained area ratio (SAR), stained path number (SPN), distribution of different preferential flow paths width and lateral flow length along the slope.【Result】Results indicated that: (1) Larger stained area ratio and more stained path number were observed in upper soil horizon than deeper soil horizon. Compared among different vegetation covers, the largest SAR was observed in SDFS, followed by DP and EG, which were 44.2%, 36.1%, and 35.3% at 0-60 cm depth, respectively. While average SPN in SDFS, EG, and DP was 43, 19, 15 at 0-60 cm depth, respectively. For different topographic positions, larger SAR was identified in upslope sites (41.5%) than in downslope sites (35.6%), while upslope sites had less SPN (23) than downslope sites (28) at 0-60 cm depth. Deeper percolated depth was identified at SDFS sites than that of other sites, which showed abundant stained paths even at 60-110 cm depth, while few paths were found at this horizon for EG and DP sites. (2) The stained area at six sites were dominated by preferential flow paths with 1-10 cm width and >10 cm width, which account for 82.8% of the total stained area. Homogeneous matrix flow and heterogeneous matrix fingering flow were mainly distributed at 0-30 cm depth, while other preferential flow patterns were mainly observed at deeper soil horizons. (3) Compared with EG and SDFS sites, more lateral flow appeared at DP sites showing stained patches extended 50 cm distance along the downslope direction, while only 10-20 cm distance extending was observed at other sites. 【Conclusion】Vegetation types and topographic position affected water infiltration processes through controlling soil properties and affecting water flow paths. Forestland sites had a better ecohydrological function in water conservation than deforested land, as the vertical flow process at DP was inhibited by the plowing hardpan. These led to more lateral flow at the shallow horizon and had more risks triggering a surface runoff. The practices of deep ploughing and reforestation can enrich root channels and benefit soil and water conservation.

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刘目兴,宋兴敏,卢世国,张海林,易 军.三峡库区不同植被覆盖坡地的土壤优先流运动特征研究[J].土壤学报,2022,59(5). DOI:10.11766/trxb202102230616 LIU Muxing, SONG Xingmin, LU Shiguo, ZHANG Hailin, YI Jun. Research on the Characteristics of Preferential Flow Movement Along Varied Hillslopes Covered with Different Vegetation in the Three Gorges Reservoir Area[J]. Acta Pedologica Sinica,2022,59(5).

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