黑土和白浆土浅沟侵蚀土壤阻力参数季节变化研究

Ephemeral gully (EG) erosion is threatening the soil resource and crop yield in the northeastern China. Critical shear stress and channel erodibility are two commonly used parameters indicating the soil resistance to EG erosion. They are also important parameters in ephemeral gully prediction models. In nature condition, they are enduring seasonal variation under the wetting-drying and other effects. However, the knowledge about this variation is still limited. In the northeastern China, there are still no scientific publications about it. This situation strongly affects the prediction of ephemeral gully erosion. Therefore, this project plans to select black soil and Albic bleached soil, two widely cultivated soils but enduring ephemeral gully erosion, as study soil. One typical ephemeral gully will be selected in each soil as study site. By dynamic sampling, whose span is 3 year and resolution is 1 month, flume experiment and soil ananlysis, research will be carried out to: illustrate the seasonal variation characteristics of critical shear stress and channel erodibility in the 2 layer (plough layer and plow pan) of 2 soils (black soil and albic bleached soil); reveal the relationship between these two parameters and other soil properties and then establish a evaluation model; preliminarily reveal the affecting mechanism of wetting-drying on these two parameters. The result of this research will further reveal the mechanism of ephemeral gully erosion and provide scientific evidence for the prediction and control of ephemeral gully erosion for the northeastern China.

浅沟侵蚀正危害着我国东北地区的土壤资源和粮食生产。临界剪切力和沟道可蚀性是反映浅沟侵蚀土壤阻力的2个常用参数，也是浅沟侵蚀预报的重要参数。自然条件下，它们在干湿交替等作用影响下存在季节变化。然而，人们对这种变化的认识还很有限，东北地区未见有针对性研究。这种现状严重影响到浅沟侵蚀的预报。因此，本项目拟选取东北地区耕地较多、存在浅沟侵蚀的黑土和白浆土作为研究对象，在每种土壤中选取1条典型浅沟作为研究区，利用持续3年、每月1次的动态土壤采样，结合水槽冲刷、土壤理化分析等手段，开展针对性研究，以查明这2种土壤（黑土、白浆土）、2个土层（耕作层、犁底层）临界剪切力和沟道可蚀性的逐月变化特征，揭示这两个参数与其他土壤属性（容重、湿度等）的定量关系，初步揭示干湿交替作用对这两个参数的影响机理。研究结果可以进一步揭示浅沟侵蚀机理，为东北地区浅沟侵蚀的预报和治理提供科学依据。

东北地区是我国重要粮食生产基地。但土壤侵蚀正危害着东北地区坡耕地，对我国粮食安全构成威胁。本项目开展了以下研究。（1）利用高精度的空间数据，查明整个东北地区及其各地貌分区、土壤类型、流域和行政区中坡耕地的面积和坡度特征。（2）利用各省土种志资料、诺谟图和径流小区资料，查明东北地区各土种、亚类、土类和整个地区的通用土壤流失方程中的土壤可蚀性（K诺谟和K小区）。（3）利用对2个小流域多年的地面调查，查明吉林省黑土区浅沟的形态特征和空间分布。（4）利用野外采样和径流冲刷实验，初步查明黑土和白浆土的浅沟侵蚀阻力系数（临界剪切力τc和和土壤可蚀性Kch）。结果显示：（1）东北地区坡耕地总面积为19.5万km2，平均坡度为3.4°。黑土区和白浆土区的坡耕地面积分别为4.8万km2和1.6万km2。（2）东北地区K诺谟平均值为0.028，K小区平均值为0.032。其中，黑土和白浆土的K诺谟均为0.035，K小区均为0.040。与我国其他地区相比，东北地区K诺谟较小，但K小区较大。K诺谟较小的主要原因是土壤粉粒含量较少和有机质较高。K小区较大可能与其较寒冷的气候、蒙脱石和伊利石含量较多的黏土矿物组成以及冻融作用有关。（3）吉林省黑土区浅沟密度平均为1.2 km/km2，平均长度为70 m，平均宽度为104 cm，平均深度为13 cm，平均横截面积为0.15 m2，平均宽深比为8.0，平均侵蚀速率为0.24 mm/a。（4）临界剪切力（τc）和土壤可蚀性（Kch）存在季节变化。τc随时间增大，Kch随时间减小。黑土的τc从6月的5.2 pa增大到8月的7.1 pa。白浆土的τc从6月的6.2 pa增大到8月的6.6 pa和10月的7.1 pa。黑土的Kch从6月的0.006 s/m减小到8月的0.005 s/m和10月的0.001 s/m。白浆土的Kch从6月的0.0015s/m减小到8月的0.014 s/m和10月的0.010 s/m。雨滴打击和干湿交替会一定程度上增大τc和减小Kch。而机械压实会显著减小Kch。10月份Kch剧烈减小部分与收割机的机械压实有关。