水保所知识产出(1956---)知识库

土壤分离是土壤侵蚀过程的起始阶段，为泥沙输移和沉积过程提供了物质准
备。它受控于坡面流水动力条件、土壤属性和植被根系的生长。在植被生长季内，
植被根系的生长会引起土壤理化性状的改变，土壤理化性状的季节变化可能影响
土壤分离过程，零星研究仅在欧洲有所报道。但以往的研究多集中于缓坡，陡坡
条件下土壤分离过程的影响机制尚不清楚。在黄土高原地区，农耕地是侵蚀泥沙
的主要来源。在黄土高原作物生长季，作物根系的生长会引起土壤理化性状的改
变，进而引起土壤分离过程发生变化，目前关于它们之间的定量关系尚不清楚，
需要开展定量研究。本研究采用变坡试验水槽系统，研究了黄土丘陵区典型农耕
地玉米、谷子、大豆和土豆土壤分离过程的季节变化及影响因素，重点探讨了土
壤属性和作物根系生长对土壤分离能力、细沟可蚀性和临界剪切力的影响。并建
立了基于土壤属性、根系密度和水动力学参数的土壤分离能力和细沟可蚀性模拟
方程，为阐明黄土高原地区土壤分离过程的水动力学机理、评价作物根系水土保
持效应、合理配置水土保持措施提供理论依据和数据支撑。主要结论如下：
（1）探讨了坡面水动力学参数、土壤属性和作物根系对土壤分离能力季节
变化的影响及其机制。随水流剪切力增大，土壤分离能力呈线性函数形式增大。
随土壤粘结力、水稳性团聚体和作物根系密度增大，土壤分离能力呈指数形式下
降。
农事活动、土壤硬化过程和作物根系密度的季节变化导致了农耕地土壤分离
能力的季节变化。黄土丘陵区农耕地的土壤分离能力在整个实验期呈现显著的先
升高再降低的季节变化趋势(p < 0.05)。土豆地的平均土壤分离能力最大(1.57±1.4
kg m -2 s -1 )，其次是玉米地(1.37±1.34kg m -2 s -1 )、大豆地(1.21±1.3kg m -2 s -1 )和谷子
地(1.15±1.31 kg m -2 s -1 )。
（2）分析了农耕地细沟可蚀性季节变化及其影响因素。随土壤粘结力、容重和作物根系密度的增大，细沟可蚀性呈指数形式降低。在黄土丘陵区作物生长
季，细沟可蚀性大致呈显著的先增加再降低的季节变化趋势（ p < 0.05）。土豆地
细沟可蚀性均值最大（0.17±0.14s m -1 ），其次是玉米地和大豆地（0.15±0.13 s m -1 ,
0.13±0.13 s m -1 ），谷子地最小（0.12±0.13 s m -1 ）。
（3）分析了农耕地土壤临界剪切力的季节变化及其影响因素。在黄土丘陵
区作物生长季，土壤临界剪切力大致呈增加的季节变化趋势。四种作物地土壤临
界剪切力季节变化在 05 . 0   水平上没有统计学显著性差异（ p ＝0.087，0.158，
0.608，0.897）。随土壤粘结力、土壤容重、水稳性团聚体和作物根系密度等参数
的季节变化，土壤临界剪切力未表现出明显的季节变化趋势。土壤临界剪切力的
季节变化规律及其影响机制有待于进一步研究。
（4）在黄土丘陵区作物生长季，利用水流剪切力、土壤粘结力和作物根系
密度分别建立了土壤分离能力和细沟可蚀性季节变化模拟方程（  NSE 0.89，
NSE ≥  0.82）；利用土壤粘结力和根系密度建立了土壤临界剪切力的季节变化模拟
方程（0.51≤ NSE ≤ 0.84）。
关键词：黄土丘陵区；土壤分离；细沟可蚀性；临界剪切力；作物根系；
季节变化

Soil detachment is the initial stage of soil erosion process, and also is the
principal sediment source of subsequent transport and deposition. It is usually affected
by a specific hydraulic condition, soil properties, and the growth of root system.
During the vegetation growing season, the growth of root system will cause the
temporal variation of soil properties. However, many of those soil properties fluctuate
greatly over time, which can certainly lead to the temporal variation in soil
detachment; previous limited studies have shown that the temporal variation in soil
detachment capacity by overland flow was only influenced by some of soil properties
in the loess belt of Europe. Nevertheless, previous researches were mainly focused on
the gentle slope, the temporal variation in soil detachment capacity by overland flow
and its influencing factors under steep slope are not fully understood yet. In the Loess
Plateau of China, soil erosion in the cultivated lands，which is considered as the
principal sediment source delivered into the Yellow River, has long been a central
concern. In the Loess Plateau, the growth of crop root system may cause the temporal
variation of soil properties. However, many of those soil properties fluctuate greatly
over time, which can certainly lead to the temporal variation in soil detachment
processes. At present, it is still unclear for the temporal variation in soil detachment
capacity by overland flow and the potential influencing factors during one growing
season.This study was carried out to determine the effects of soil properties and crop
roots on soil detachment process in maize (Zea mays L.), millet (Setaria italica),
soybean (Glycine max), and potato (Solanum tuberosum L.), investigate temporal
variation in soil detachment and its influencing factors, and establish soil detachment  model based on a specific hydraulic condition, soil properties, and the growth of root
system. Soil detachment capacity was measured in a hydraulic flume with adjustable
bed gradients. This study can provide useful information for revealing soil detachment
mechanism, evaluating the soil and water conservation function of crop root system,
and arranging soil and water conservation practice properly. The mainly results of this
study are listed as below:
(1) This study discussed the effects of erosion power, soil properties, and crop
root on soil detachment capacity. The results indicated that soil detachment capacity
linearly increased with increasing shear stress. With increasing soil cohesion,
water-stable aggregate and crop root density, soil detachment capacity reduced as an
exponential function.
The temporal variations of soil detachment capacity were affected by tillage
practices, soil consolidation, water-stable aggregates, and root growth. Soil
detachment capacity for each crop fluctuated significantly over time with a similar
pattern of the temporal variation following increased firstly, then decreased (p < 0.05)
during one growing season in the Loess Plateau. The measured mean D c was greatest
for potato (1.57±1.4 kg m -2 s -1 ), followed by maize (1.37±1.34kg m -2 s -1 ), soybean
(1.21 ±1.30kg m -2 s -1 ), and millet (1.15±1.31 kg m -2 s -1 ).
(2) This study revealed the temporal variation in soil rill erodibility and its
influencing factors. The decline of soil rill erodibility could be explained by the
increasing of crop root density, bulk density, and soil cohesion using an exponential
function. Soil rill erodibility for each crop fluctuated significantly over time with a
similar pattern of the temporal variation following increased firstly, then decreased
during one growing season in the Loess Plateau (p < 0.05). The measured mean K r
was greatest for potato (0.17±0.14s m -1 ), followed by maize (0.15±0.13s m -1 ),
soybean (0.13±0.13 s m -1 ), and millet (0.12±0.13s m -1 ).
(3) This study revealed the temporal variation in soil critical shear stress and its
influencing factors. No significant temporal variation in soil critical shear stress for
each crop was found during one growing season（ p ＝0.087，0.158，0.608，0.897）
following the temporal variation of soil cohesion, bulk density, water-stable
aggregates, and root growth. Further studies are needed to investigate the potential
effects of soil properties and root growth on critical shear stress.
(4)The prediction model of soil detachment capacity and soil rill erodibility
based on shear stress, soil cohesion, and root density were established（  NSE 0.89， NSE ≥ 0.82）. The prediction model of soil critical shear stress based on soil cohesion
and root density was established（0.51≤ NSE ≤ 0.84）.
Key words ：Soil detachment ； Rill erodibility ； Critical shear stress ；
Crop system ；Temproal Variation