植被发育玄武岩斜坡土体基质吸力及其影响因素

Soil Matric Suction and Its Influencing Factors on a Well Vegetated Basalt Slope

植被发育斜坡非饱和带垂直深度〈50 cm范围内根系密布,与根系相关的大孔隙很大程度上降低了土体密实程度,而垂直深度〉50 cm范围内根系稀疏,土体较密实,孔隙比较小。基质吸力受土体孔隙分布影响显著。对昆明呈贡县某植被发育玄武岩斜坡垂直深度10～20 cm和60～80 cm处取原状样（编号为XA和XB）进行了基质吸力测试,结果表明相同含水率下基质吸力XA小于XB。对头寨沟滑坡左翼某植被发育玄武岩斜坡垂直深度10～20 cm和60～80 cm处取原状样（编号为TA和TB）也进行了基质吸力测试,结果表明相同含水率下基质吸力TA〉TB。对研究区土体有机质含量测试发现,TA、TB分别为14.89%、3.28%,而XA、XB分别为1.05%、0.39%。土壤有机质自身结构疏松多孔,并且会增大土壤比表面积和毛管孔隙度,改善颗粒级配和土体结构,使土壤吸附作用增强,利于土壤水分的保持,进而影响到土体土-水特征曲线。

Plant roots are densely scattered in soil shallower than 50cm of unsaturated zone on a vegetated slope. Those related soil macro pores substantially reduce soil compaction,while in region deeper than 50 cm, soil density is much larger and its porosity smaller. Soil matric suction is significantly affected by pore distribution. This paper takes undisturbed samples（ No. XA and XB） from vertical depth 10 -20 cm and 60 -80 cm of a vegetated basalt slope of Chenggong Kunming, it then tests the matric suction of the samples, and the results show that XA is less than XB in matric suction when the moistures are the same. This paper further more takes undisturbed samples （No. TA and TB） from vertical depth 10 - 20 cm and 60 -80 cm of a vegetated basalt slope beside Touzhai Landslide, and conducts a matric suction experiment. The results show that TA is greater than TB in matric suction when the moistures are the same. Test against the organic matter content of experimental zones finds that TA and TB are 14.89% and 3.28% respectively,while XA,XB are 1.05% and 0.39%. Since the structure of soil organic matter is porous, it thus enlarges surface area and capillary porosity of the soil, which in turn enhances particle grade and soil structure. Thus absorption ability of the soil is strengthened, which is beneficial to moisture retention of soil and affects the soil water characteristic curve （SWCC）.