Geometric distribution characteristics and mechanical reinforcement effect of herbaceous plant roots at different growth periods

Abstract

The growth form of herbaceous plant roots and their mechanical reinforcement effect on soil play a positive role in preventing soil erosion. Herbaceous plant roots grow with increasing growth periods, thus resulting in different root geometry and mechanical reinforcement in different growth periods. To explore the difference in root system characteristics of herbaceous plants and their effect on soil reinforcement in different growth periods, two herbaceous plants, Chenopodium album, and Setaria viridis, were taken as the research objects. First, the diameters of the two herbaceous plant roots in each growth period were measured by pixel conversion, and then the root area ratio (RAR) was calculated, and the tensile force of the roots in each growth period was measured with a tensile force meter. The measurement results were substituted into the Wu-Waldron model (WWM), and the WWM was corrected by the direct shear test. The modified WWM was used to calculate the mechanical reinforcement effect of roots at different growth periods. Second, the average root area ratio (ARAR) and the average root additional cohesion (Acr) in different growth periods of the two herbaceous plants were calculated. Finally, to characterize the reinforcement effect of herbaceous plant roots in different growth periods, FLAC3D was used to simulate the compressive strength of the root-soil composite in the unconfined compressive state. The results showed that the RAR of Chenopodium album and Setaria viridis increased with the increase of the growth period, and the standard deviation of RAR after 78d was higher than that in the previous period. The root tensile force of Chenopodium album on 14d and Setaria viridis on 21d was the smallest, and the tensile force of roots increased significantly after continued growth for 7d, and the effect of further growth was not obvious. The root additional cohesion of Chenopodium album and Setaria viridis fluctuated with increasing growth periods. The ARAR and Acr of Chenopodium album and Setaria viridis increased with the increase of the growth period and showed a significant positive correlation (p < 0.01). With the increase in the growth period, the compressive strength of the root-soil composite increased linearly. When the herbaceous plant grew to 131d, the compressive strength of the root-soil composite of Chenopodium album and Setaria viridis increased by 24% and 21% compared with that of the rootless soil. This study can provide a reference for the study of using the mechanical reinforcement of herbaceous plant roots to inhibit soil erosion.