Study On The Adaptation Of Salt-tolerant Plants And Their Roots’ Soil Fixation Characteristics

The new Chengkun Railway Sedan Tunnel dump in Heijing Town,Lufeng County,Yunnan Province,is rich in gypsum,mannite and chloride salts.Salt-tolerant plants are able to adapt to normal growth under saline stress and reduce the concentration of soil salt particles.The plant roots have strong tensile strength and can improve the shear strength of the soil.The planting of salt-tolerant plants on the slopes of dumpsites can both manage saline soils and stabilise the slopes.This paper investigates the adaptability of salt-tolerant plants and their root fixation characteristics in salt rock dumps through on-site investigation of salt-tolerant plants in dumps,determination of root content in different soil layers,detection of p H and electrical conductivity of inter-root soil solutions,single-root tensile strength test and shear test of soil containing roots,and the main research results achieved are as follows:1.A typical sample site was selected according to the experimental program,and the vegetation survey of the disposal site was completed.Through the investigation of the vegetation on the saline slope of the disposal site,20 species of vegetation were found in the disposal site,3 species of trees,4 species of shrubs and 13 species of herbs,belonging to 12 families and 20 genera.Gramineae,Asteraceae,Leguminosae and Solanaceae vegetation are dominant,accounting for 60% of the total number of species,among which Gramineae occupies a dominant position,accounting for 30% of the total number of species.At present,the vegetation species of the dump site are still mainly herbaceous plants,followed by shrubs,with the least number of trees,and the community succession is still incipient succession.The dominant species are mainly salt-tolerant plants,such as herbaceous plants Oxalis,ghost needle grass,horse mudra,shrubs halberd leaf acid mold,trees silver acacia and so on.Salt-tolerant plants can grow and develop normally in saline soils and restore the ecology of the slope of the disposal site.2.According to the results of the vegetation survey of the disposal site,the dominant salt-tolerant herbaceous plant Oxalis,shrubs and trees were selected for the study,and the sampling area was delineated and the samples were taken along the vertical profile of the soil layer.The root diameters of the three salt-tolerant plants were measured in the range of0-2 mm,0-10 mm and 0-20 mm.The 0-2 mm diameter of the root systems of different salttolerant plant types were linearly or exponentially related to the increase of soil depth.The total root content at different diameter levels of different salt-tolerant plant root systems was exponentially related to the depth of the soil layer.3.On the basis of measuring the distribution of salt-tolerant plant roots,the inter-root soil was collected in layers and then shaken off by the method.The mean values of soil p H and electrical conductivity were 0.17,0.38,and 0.55,respectively,and 0.17,0.31,and 0.46,respectively,compared with those of bare ground.The p H and conductivity of the interrooted soil of the three salt-tolerant plants increased with the depth of the soil layer.Compared with the bare ground,the changes of inter-root soil p H and conductivity of the three salt-tolerant plants were highly correlated with the root content of each soil layer.4.Oxalis root system,hastate mold root system and silver acacia root system were selected in the sample area and single root tensile strength test was completed in the laboratory.The results showed that the plant root systems had strong tensile strength.The tensile strength of all three different salt-tolerant plant root systems increased with increasing root diameter,and the tensile strength decreased with increasing root diameter.The average tensile strength of single roots of different salt-tolerant plants differed,with Oxalis maximus,Hasturtium spp.second and Silver Acacia the smallest.5.Under the natural water content,the cohesion and internal friction angle of both bare and root-bearing soils increased with the increase of soil depth.Relative to bare ground,salt-tolerant plant roots could significantly increase the shear strength of soil and increase the cohesion and internal friction angle of soil;25%,50%,75% and 100% of roots of 0-2 mm diameter class were increased above the natural root content,respectively.With the increase of soil root content,the shear strength of the soil increased,and the increase of soil cohesion was greater than the increase of internal friction angle;with the increase of soil root content,the rate of increase of soil cohesion and internal friction angle gradually slowed down and became slow;the rate of increase of soil cohesion and internal friction angle was a power function relationship with the increase of soil root content;the increase of soil cohesion and internal friction angle tended to level off and was a power function relationship.