摘要: 目的为探究金沙江干热河谷冲沟系统优先流影响下的土壤可蚀性差异规律，揭示冲沟发育区土、水相互作用机理，为干热河谷地区水土流失治理及生态恢复提供理论依据、�/sec> 方法在干热河谷典型冲沟发育区选择完整冲沟作为研究对象，基于染色示踪、土壤抗冲抗蚀及土壤理化试验，利用主成分分析等统计分析方法获取土壤优先流、土壤可蚀性指标及其相关关系，明晰集水区、沟壁、沟床、沟底完整冲沟系统土壤优先流特征，探究优先流和土壤可蚀性之间的关系、�/sec> 结果干热河谷冲沟优先流类型以“大孔隙流”为主，伴随“指流”和“漏斗流”，优先流百分数呈集水区 > 沟壁 > 沟床 > 沟底，说明冲沟上游优先流发育程度高于下游。冲沟内优先流区有机质含量、土壤含水率均高于基质流区，机械组成黏粒、粉粒、砂粒配比优先流区优于基质流区，土壤密度优先流区低于基质流区。冲沟内优先流区土壤抗冲系数小于基质流区，表明优先流会使土壤稳定性降低，抗蚀指数呈优先流区大于基质流区，说明土壤水分溶质运移会使局部土壤抗蚀性提高。冲沟系统土壤可蚀性因子（ K）与优先流百分数、优先流区染色面积比、最大染色深度均呈正相关关系，同时主成分分析显示以上3个因子是影响土壤可蚀性的主要因子、�/sec> 结论优先流发育程度高的土层中优先流区 K值总是大于基质流区，在优先流发育不足土层中则相反，优先流发育一定程度上会提高土壤可蚀性、�/sec>

关键诌�
• 干热河谷/
• 冲沟/
• 优先流区/
• 基质流区/
• 土壤可蚀�?/a>

Abstract: ObjectiveThis paper aims to explore the patterns of soil erodibility variation under the influence of preferential flow in the gully system of Jinsha River Dry Hot Valley, and in doing so, revealing the interaction mechanism between soil and water in the gully development area, so as to provide a theoretical basis for soil and water loss control and ecological restoration in dry hot valleys. MethodA complete gully in a typical gully development area of the dry hot valley was selected as the research object. Based on dye tracing, soil erosion resistance and soil physicochemical experiments, statistical analysis methods such as principal component analysis (PCA) were used to obtain the soil preferential flow, soil erodibility indicators and their correlations, clarify the soil preferential flow characteristics of the complete gully system at the catchment area, gully wall, gully bed and gully bottom, as well as explore the correlation between preferential flow and soil erodibility. ResultThe findings showed that the preferential flow in the gully of the dry hot valley was mainly “macropore flow�? accompanied by “finger flow� and “funnel flow�? Preferential flow percentages in catchment > gully wall > gully bed > gully bottom. This indicated that the development degree of preferential flow in the upstream of the gully was higher than that in the downstream. Moreover, the gully’s preferential flow area also featured higher organic matter and soil moisture contents, better mechanical composition (clay, silt and sand), and lower soil bulk density relative to those in the matrix flow area. Also to take note is that the soil anti-scour coefficient in the gully’s preferential flow area was smaller compared with that in the matrix flow area, suggesting that the preferential flow can reduce soil stability. Furthermore, the erosion resistance index of each gully section in the preferential flow area was higher than that in the matrix flow area, indicating that soil water and solute transport can improve local soil erosion resistance. The soil erodibility factor ( K) of the gully system was positively correlated with the percentage of preferential pathway, the dry coverage of preferential pathway and the maximum dyed depth. Additionally, PCA showed that the above three factors were all the main factors affecting soil erodibility. ConclusionIn soil layers with high preferential flow development, the Kin the preferential flow area is always higher than that in the matrix flow area, which is contrary to the soil layer with insufficient preferential flow development. This implies that the development of preferential flow improves soil erodibility to some extent.

Key words:
• dry hot valley/
• gully/
• preferential flow area/
• matrix flow area/
• soil erodibility

�?nbsp; 1研究区及采样点位�?/p>

A、B、C、D分别代表集水区、沟壁、沟床、沟底，1�?�?表示3次重复试验。A, B, C, D represent the catchment area, gully wall, gully bed, gully bottom, respectively; 1, 2, 3 indicate three repeated tests.

Figure 1.Location of the study area and sampling sites

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�?nbsp; 2染色试验及染色剖面处理图

Figure 2.Dyeing experiment and dyeing profile treatment

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�?nbsp; 3土壤基本特�?/p>

A、B、C、D分别代表集水区、沟壁、沟床、沟底，R、W分别代表优先流区和基质流区。不同小写字母表示同一土层不同样地间显著性差异（P�?.05）。同�?� A, B, C, D represent the catchment area, gully wall, gully bed, gully bottom, respectively; R, W represent the preferential flow area and the matrix flow area, respectively. Different lowercase letters indicate significant differences between different sites in the same soil layer (P< 0.05). Same as table 2.

Figure 3.Basic soil properties

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�?nbsp; 4冲沟不同部位土壤垂直剖面染色国�/p>

A、B、C、D分别代表集水区、沟壁、沟床、沟底，1 ~ 3表示该区3次重复试验。A, B, C, D represent the catchment area, gully wall, gully bed, gully bottom, and 1�? indicate three repetitions of the experiment, respectively.

Figure 4.Soil vertical profile staining of different parts of the gully

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�?nbsp; 5冲沟不同部位土壤剖面染色面积比随土层的变匕�/p>

1 ~ 3表示3次重复试验剖面，4表示3个剖面的平均值�?�? represent the three replicate test profiles, and 4 represents the average of the 3 profiles.

Figure 5.Variation of soil profile staining area ratio in different parts of gullies with soil layers

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�?nbsp; 6优先流区和基质流区抗冲系�?/p>

小写字母不同表示不同分区差异显著＇�i>P< 0.05）。Different lowercase letters indicate significant differences between different partitions (P< 0.05).

Figure 6.Impact resistance coefficients of preferential flow area and matrix flow area

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�?nbsp; 7土壤抗蚀指数动态变化过稊�/p>

Figure 7.Dynamic change process of corrosion resistance index

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�?nbsp; 8优先流和基质流区土壤可蚀�?i>K值变化图

大写字母不同表示不同土层差异显著＇�i>P< 0.05），小写字母不同表示不同分区差异显著＇�i>P< 0.05）。Different capital letters indicate significant differences between varied soil layers (P< 0.05), different lowercase letters indicate significant differences between different partitions (P< 0.05).

Figure 8.Variation of soil corrosionKvalues in the preferential flow area and matrix flow area

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�?nbsp; 9冲沟不同部位优先流因子与土壤可蚀性的主成分分枏�/p>

Figure 9.Principal component analysis of preferential flow factor and soil corrosivity in different parts of the gully

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�?nbsp; 1样地基本情况

Table 1.Basic situation of the sample plots

样点 Sample point	坡度 Slope/（°）	海拔 Elevation/m	盖度 Coverage/%	土壤含水� Soil water content/%	密度 Bulk density/（g·m�?（�/td>	土壤质地 Soil texture/%
						黏粒 Clay	粉粒 Silt	砂粒 Sand
集水� Catchment area	7	1 109.54	80	10.36	1.56	10.33	37.29	52.38
沟壁 Gully wall	15	1 104.10	40	16.12	1.80	9.57	33.07	57.36
沟床 Gully bed	12	1 096.19	65	13.54	1.43	4.70	19.75	75.55
沟底 Gully bottom	6	1 092.33	75	5.14	1.43	4.62	15.06	80.32

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�?nbsp; 2冲沟区不同部位土壤垂直剖面优先流指标统计分析

Table 2.Statistical analysis of preferential flow indexes of soil vertical profile in different parts of the gully area

优先流指� Preferential flow index	样地名称 Sample plot name
	集水� Catchment area	沟壁 Gully wall	沟床 Gully bed	沟底 Gully bottom
染色面积� Dyeing area ratio/%	27.85 ± 0.56d	42.93 ± 1.49b	50.55 ± 3.89a	40.02 ± 2.77bc
基质流深� Matrix flow depth/cm	4.69 ± 1.66d	11.06 ± 1.44bc	16.93 ± 2.75a	13.28 ± 0.88ab
最大染色深� Maximum dyeing depth/cm	42.47 ± 0.91a	41.96 ± 1.21a	43.45 ± 1.34a	38.40 ± 1.92a
优先流区染色面积� Dyeing area ratio of preferential flow area/%	18.90 ± 4.33a	23.34 ± 3.98a	18.61 ± 2.40a	12.46 ± 1.74b
优先流百分数 Percentage of preferential flow/%	64.68 ± 2.78a	46.96 ± 3.58b	32.08 ± 2.32c	31.55 ± 2.45c
注：表中数据为“平均� ± 标准差”� Note: data in the table are “mean ± standard deviation�?

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�?nbsp; 3优先流指标与土壤可蚀性相关分枏�/p>

Table 3.Correlation analysis between preferential flow indicators and soil erodibility

土壤可蚀性指� Soil erodibility index	优先流指� Preferential flow index	相关系数 Correlation coefficient	P
K	染色面积� Dyeing area ratio (X1)	�?.453	0.078
	基质流深� Matrix flow depth (X2)	�?.634	0.008
	最大染色深� Maximum dyeing depth (X3)	0.588	0.017
	优先流区染色面积� Dyeing area ratio of preferential flow area (X4)	0.522	0.038
	优先流百分数 Percentage of preferential flow (X5)	0.668	0.005

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�?nbsp; 4优先流指标对K值影响的主成分分枏�/p>

Table 4.Principal component analysis of the impact of preferential flow index onKvalue

主成刅�br/>Principal component	特征倻�br/>Eigenvalue	方差贡献玆�br/>Variance contribution rate/%	方差累计贡献玆�br/>Cumulative contribution rate of variance/%	X1	X2	X3	X4	X5
1	3.58	59.64	59.64	�?.37	�?.45	0.30	0.31	0.51
2	1.58	26.38	86.02	0.56	0.32	0.51	0.54	�?.06
3	0.51	8.43	94.45	�?.14	0.13	0.60	�?.63	�?.28

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