Mechanism Of The Microstructure Of A Single Root To The Tensile Properties Of Plant Root System

The mechanics of soil reinforced by tree roots is a multidisciplinary hot issue and vital to soil erosion prevention and slope protection. This study chose the roots of13common tree species of northern China, shrubs, herbal as research objects and used mathematical and statistical methods like variance analysis and multivariate statistical analysis to compare the single tensile properties among different species systematically based on the theories such as wood science, biology and materials mechanics in order for the better choice of species for slope stabilization; besides, this is the first time to discuss the relationship between of the single root tensile properties and the microstructure of13species in3broad categories from the microstructural perspectives so as to reveal the internal mechanism of different plant species reinforcing soil comprehensively.The main research results are as follows:(1) Ulmus pumila was the strongest in maximum tensile resistance and tensile strength of the13research species,and was successively followed by Betula platyphylla.Quercus mongolica,Myripnois dioica,Pinustabulaeformis,Corylus mandshurica,Larix principis-rupprechtii,Weigela florida,Rosa davurica,Cirsium setosum,Rhododendron micranthum,Artemisia scoparia, Artemisia sacrorum; the difference of roots tensile properties in different species is significant.(2)The maximum tensile strengths of all the13species increased with increasing diameter and showed a power function positive correlation, follow the power function; while their tensile strengths decreased with the increase of the diameter and were in negative correlation,followed the power function. (3) Gauge and stretching rate had a significant effect on the tensile characteristics of shrubs; while stretching rate had litter effect on the tensile characteristics of herbs.(4)The results showed the relationship between the single root tensile characteristics and the microstructure of single root of Ulmus pumila, Betula platyphylla, and Quercus mongolica-which were broad-leaf species:among the9possible factors that may affect the root system tensile properties, area percentage of wood fiber in secondary xylem, area percentage of phloem, length of wood fiber, wall cavity ratio and aspect ratio of wood fiber had a positive impact on the root system tensile properties, while the impact was different respectively; area percentage of wood fiber had the largest impact on root system tensile resistance; area percentage of phloem determined the value of single root tensile strength of different tree species; the size of wood fiber had an effect on both single root tensile resistance and tensile strength, therein aspect ratio of wood fiber was the most influential.(5) The result showed the relationship between the single root tensile characteristics and the microstructure of Pinus tabulaeformis and Larix principis-rupprechti which were coniferous species:area percentage of tracheid in cross section of root system, length and aspect ratio of tracheid were positively correlated with single tensile characteristics, while the area percentage of tracheid of the two species was indifferent; length of tracheid was a very important factor to determine the tensile strength of root system, which was that the longer the tracheid was, the larger the aspect ratio was, and the larger the maximum tensile strength of root system was, while the size of tracheid and the diameter of root were not link essentially in the same species; tracheid microfibril angle was the most significant factor that influenceed the root system tensile strength and there was a negative linear correlation between them, which was the smaller the tracheid microfibril angle was, the larger the single root tensile strength was; tracheid microfibril angle increased with the increasing of root diameter.(6) The result showed the relationship between the single root tensile characteristics and the microstructure of Myripnois dioica, Coiylus mandshurica, Rosa davurica, Weigela florida and Rhododendron micranthum-which were shrubs:area percentage and wall cavity ratio of wood fiber had a positive correlation with the maximum tensile resistance of shrubs; area percentage of wood fiber, area percentage of phloem and wall cavity ratio of wood fiber was positively correlated with the single root tensile strength, there in area percentage of phloem was the most significant.(7) The result showed the relationship between the single root tensile characteristics and the microstructure of Artemisia scoparia, Cirsium setosum and Artemisia sacrorum-which were herbs: area percentage and wall cavity ratio of wood fiber was positively correlated with the maximum tensile resistance and tensile strength of the single root of shrubs; however, because of the indifference of the increase of area percentage and wall cavity ratio of wood fiber with the increase of root diameter in the same species, they only can determine the difference of root system tensile properties among different species rather than explaining the cause of the change that the root tensile resistance and tensile strength with the largest diameter.