Root System Architecture and Tensile Mechanical Properties of Dominant Spontaneous Herbs in the Linpan of Western Sichuan

As a typical traditional rural settlement unit on the Chengdu Plain, Linpan in Western Sichuan, hereafter referred to as Linpan, is not only a representative form of local rural settlement, but also reflects the distinctive topographic pattern and ecological characteristics of the region. At present, Linpan landscapes are facing the dual threats of ecological degradation and soil erosion. Therefore, this study selected six dominant natural herb species in Linpan settlements in Pidu District, Chengdu, namely the fibrous-rooted species Galinsoga parviflora and Erigeron annuus, and the taprooted species Solanum nigrum, Achyranthes aspera, Artemisia argyi, and Erigeron canadensis. The differences in root architecture and tensile mechanical properties between the growing season and the dormant season were analyzed, and their soil reinforcement capacity was comprehensively evaluated, so as to provide a scientific basis for plant selection in ecological restoration and soil erosion control in Western Sichuan Linpan landscapes. The results show that: (1) Except for the root branching pattern of Achyranthes aspera, which was close to the herringbone type, the root systems of the other species tended more toward dichotomous branching. Among them, Erigeron annuus had no distinct taproot, and the lengths and angles of its root branches at different orders were similar, reflecting its root adaptability as a pioneer species. The root systems of Galinsoga parviflora and Solanum nigrum were characterized by notably high total numbers of root bifurcations, indicating their strong pre-adaptive capacity for resource preemption. (2) In the growing season, the tensile strength (18.2 MPa) and elastic modulus (348.29 MPa) of single roots of Galinsoga parviflora were the highest, while in the dormant season, the tensile strength (45.89 MPa) and elastic modulus (670.17 MPa) of single roots of Artemisia argyi were significantly higher than those of the other species. The root systems of these two species showed the greatest potential for soil reinforcement. (3) Both root tensile strength and elastic modulus showed a highly significant negative correlation with root diameter, confirming that fine roots play a decisive role in enhancing soil reinforcement capacity. In summary, the root systems of Galinsoga parviflora and Artemisia argyi showed the best overall performance in soil reinforcement, forming a natural complementarity across growth stages. In ecological restoration practices for Linpan landscapes, the natural populations of these two species can be prioritized for conservation through enclosure management, disturbance control, and other measures, thereby enabling their soil and water conservation functions to be realized in a low-cost and efficient manner.