| Plant roots play a dominant role in slope ecological protection.Different plant root architectures and single root tensile properties under slope conditions are studied,from the perspective of root system,the selection and configuration of slope vegetation restoration plants are proposed to provide theoretical guidance for slope vegetation restoration.In this study,erosion troughs were used to simulate a 45° slope,and 11 plants with strong resistance and adaptability were selected as the research objects through data query and previous survey results,it includes Cerasus humilis(Bge.)Sok.,Lespedeza bicolor Turcz.,Rhus chinensis Mill.,Indigofera pseudotinctoria Matsum.,Amorpha fruticosa L.,Rosa xanthina Lindl.,Vitex negundo L.,Ziziphus jujuba Mill.,Caragana korshinskii Kom.,Astragalus adsurgens Pall.,Medicago Sativa L.,to study the root architecture characteristics and root structure types of plants,and to study single root tensile of 11 plants,in order to explore the correlation between single root tensile resistance,single root tensile strength,single root strain and root diameter of different roots and different plant species.Finally,the principal component analysis method was used to comprehensively analyze the root architecture and mechanical related indicators to select the plants with the best effect of slope protection and soil fixing capacity.The main results are as follows:(1)The root systems of Cerasus humilis(Bge.)Sok.,Rhus chinensis Mill.,Lespedeza bicolor Turcz.were more evenly distributed in the Down-slope direction and Up-slope direction,and the distribution range was wider,the root system of Ziziphus jujuba Mill.,Caragana korshinskii Kom.and Medicago Sativa L.had no distribution in the up-slope direction or the distribution range was small;The root/shoot ratio of Cerasus humilis(Bge.)Sok.,Amorpha fruticosa L.,Vitex negundo L.,Ziziphus jujuba Mill.,Medicago Sativa L.were all greater than 1;the total number of roots of the four plants of Cerasus humilis(Bge.)Sok.,Lespedeza bicolor Turcz.,Astragalus adsurgens Pall.,Amorpha fruticosa L.are larger,all of which can reach level IV lateral roots,which means the branching ability was stronger,and the four plants had better performance in root length,root surface area,and root volume characteristics than other plants,and the fine roots were also more developed;Cerasus humilis(Bge.)Sok.,Amorpha fruticosa L.,Rosa xanthina Lindl.,Vitex negundo L.,Astragalus adsurgens Pall.showed a large proportion of inclined roots,Rhus chinensis Mill.,Lespedeza bicolor Turcz.,Indigofera pseudotinctoria Matsum.showed a large proportion of horizontal roots.Except for the main roots of the Cerasus humilis(Bge.)Sok.,there were no main roots;For each plant,the root length of different diameter grades accounts for the proportion of the total root length,which showed that the fine roots were much larger than the middle roots,and the proportion of coarse roots were the smallest;the root topology index of Ziziphus jujuba Mill.,Caragana korshinskii Kom.,Medicago Sativa L.were close to 1,the closer it was the herringbone branch,although the three plants had obvious main roots,but the amount of lateral roots were less;the topological index of the root system of Cerasus humilis(Bge.)Sok.,Lespedeza bicolor Turcz.,Astragalus adsurgens Pall.was close to 0.5,the closer the root system was to the pattern of forked branches.(2)11 plants root systems showed a total of four root structure types,namely R type,VH type,V type and M type.The root structure of Lespedeza bicolor Turcz.,Rhus chinensis Mill.,Indigofera pseudotinctoria Matsum.were VH type;the root structure of Amorpha fruticosa L.,Rosa xanthina Lindl.,Vitex negundo L.,Astragalus adsurgens Pall.were R type;the root structure of Ziziphus jujuba Mill.,Caragana korshinskii Kom.,Medicago Sativa L.were V type;Cerasus humilis(Bge.)Sok.was of M type root structure.(3)The tree species and diameter had a significant effect on the tensile resistance of single root.with the increase of root diameter,the tensile resistance of single root of 11 plants all increased significantly,and all showed a power function,but there was a certain difference in the increment.By comparing the average maximum single root tensile resistance of 11 plants,the order was as follows: Amorpha fruticosa L.(157.03 N)> Lespedeza bicolor Turcz.(154.72 N)> Ziziphus jujuba Mill.(117.3 N)> Indigofera pseudotinctoria Matsum.(92.76 N)> Vitex negundo L.(87.05 N)> Cerasus humilis(Bge.)Sok.(86.78 N)> Medicago Sativa L.(84.61 N)> Rosa xanthina Lindl.(81.72 N)> Astragalus adsurgens Pall.(70.95 N)> Caragana korshinskii Kom.(50.89 N)> Rhus chinensis Mill.(34.62 N).Except that the change trend of single root tensile strength of Cerasus humilis(Bge.)Sok.with root diameter was not obvious,the single root tensile strength of the remaining 10 plants all decreased with increasing root diameter,and the root diameter when the single root tensile strength was maximum both were less than 1 mm.The single root tensile strength of different plants was different from the function of root diameter,the single root tensile strength of five kinds of plants,such as Ziziphus jujuba Mill.,Lespedeza bicolor Turcz.,Rhus chinensis Mill.,Cerasus humilis(Bge.)Sok.,Medicago Sativa L.,decreased logarithmically with the increase of root diameter;the single root tensile strength of five species of Indigofera pseudotinctoria Matsum.,Astragalus adsurgens Pall.,Amorpha fruticosa L.,Caragana korshinskii Kom.,Rosa xanthina Lindl.decreased with the increase of root diameter;there was no obvious trend between the single root tensile strength of the Vitex negundo L.and the root diameter,but when the root diameter of the Vitex negundo L.was greater than 1 mm,its single root tensile strength tended to decrease with the increase of the root diameter.By comparing the average maximum single tensile strength of 11 plants,the order was Vitex negundo L.(46.98 MPa)>Caragana korshinskii Kom.(37.05 MPa)>Indigofera pseudotinctoria Matsum.(20.88 MPa)>Ziziphus jujuba Mill.(19.57 MPa)>Rosa xanthina Lindl.(18.01 MPa)>Medicago Sativa L.(16.54 MPa)>Amorpha fruticosa L.(16.19 MPa)>Cerasus humilis(Bge.)Sok.(14.13 MPa)>Lespedeza bicolor Turcz.(10.61 MPa)>Astragalus adsurgens Pall.(8.92 MPa)>Rhus chinensis Mill.(4.74 MPa).The single root strain of 6 plants of Cerasus humilis(Bge.)Sok.,Rosa xanthina Lindl.,Vitex negundo L.,Ziziphus jujuba Mill.,Caragana korshinskii Kom.,Medicago Sativa L.had a good correlation with the root diameter,and their correlation coefficients were all greater than 0.5,but the single root strain of these 6 plants with the change trend of root diameter,the single root strain of Cerasus humilis(Bge.)Sok.root system gradually decreased with the increase of root diameter,while the single root strain of the remaining 5 plants increased with the increase of root diameter.There was no obvious functional relationship between the single root strain and root diameter of the five plant species of Lespedeza bicolor Turcz.,Rhus chinensis Mill.,Indigofera pseudotinctoria Matsum.,Amorpha fruticosa L.,Astragalus adsurgens Pall..The root diameter increased first and then decreased of Lespedeza bicolor Turcz.,Indigofera pseudotinctoria Matsum.,Astragalus adsurgens Pall..The single root strain of some roots of Rhus chinensis Mill.and Rosa xanthina Lindl.were relatively small,which made the root system easy to break.Using the principal component analysis method,the comprehensive slope protection effect of 11 plants was obtained as follows: Cerasus humilis(Bge.)Sok.>Lespedeza bicolor Turcz.>Astragalus adsurgens Pall.>Amorpha fruticosa L.>Medicago Sativa L.>Rhus chinensis Mill.>Indigofera pseudotinctoria Matsum.>Vitex negundo L.>Rosa xanthina Lindl.>Ziziphus jujuba Mill.>Caragana korshinskii Kom..Among them,the comprehensive principal component of Cerasus humilis(Bge.)Sok.is the best,the comprehensive slope protection effect is the best,and the comprehensive ranking of Caragana korshinskii Kom.is the worst.The underdeveloped root system restricts its slope protection ability. |
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