Effects of root morphological traits on soil detachment for ten herbaceous species in the Loess Plateau

Authors: WANG, BING - Northwest A&f University; LI, PAN-PAN - Northwest A&f University; Huang, Chi Hua; LIU, GUO-BIN - Northwest A&f University; YANG, YAN-FEN - Northwest A&f University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2020
Publication Date: 9/12/2020
Citation: Wang, B., Li, P., Huang, C., Liu, G., Yang, Y. 2020. Effects of root morphological traits on soil detachment for ten herbaceous species in the Loess Plateau. Science of the Total Environment. 754. Article 142304. https://doi.org/10.1016/j.scitotenv.2020.142304.
DOI: https://doi.org/10.1016/j.scitotenv.2020.142304

Interpretive Summary: Plants affect soil erosion and sediment transport, but the effects from the above-ground parts, i.e., plant canopy and surface residue, on erosion are well documents. Plant root systems can also affect erosion, but it effect is not well quantified. In this study, we quantified how the root morphology of herbaceous plants affected soil detachment process. A total of 300 undisturbed soil samples were collected from fields with 10 herbaceous plants at the Chinese Loess Plateau. These undisturbed soil samples were scoured with flowing water to measure their soil detachment capacities under six levels of flow shear stress. The root traits were measured, and erodibility parameters were estimated. The results showed that root morphology varied greatly among the ten selected herbages and plants with fibrous roots were more effective than those with tap roots in reducing soil detachment. We also found that the root surface area density was the most important factor affecting soil detachment. We propose a simple equation to estimate soil detachment capacity when the plant root parameters and soil properties were limited. This research provides new dataset and equation that can be incorporate into process-based erosion prediction models.

Technical Abstract: Plant root systems can greatly reduce soil loss, and their effects on soil erosion differ across species due to their varied root traits. The purpose of this study was to determine the effects of root morphology traits of herbaceous plants on the soil detachment process. Ten herbaceous plants in the Loess Plateau were selected, and 300 undisturbed soil samples were scoured with flowing water to measure their soil detachment capacities under six levels of shear stress (4.98 to 16.37 Pa). Then, the root traits of each soil sample were measured, and the rill erodibility and critical shear stress were estimated based on the Water Erosion Prediction Project (WEPP) model. The results showed that root morphology traits varied greatly among the ten selected herbages. Accordingly, resulting variations in soil detachment capacity (0.030 to 3.297 kg/m2/s), rill erodibility (0.004 to 0.447 s/m), and critical shear stress (4.73 to 1.13 Pa) were also observed. Plants with fibrous roots were more effective than those with tap roots in reducing soil detachment. Their mean soil detachment capacity and rill erodibility were 93.2% and 93.4 % lower, respectively, and their mean critical shear stress was 1.15 times greater than that of the herbaceous plants with tap root systems. Of all the root traits, root surface area density was the primary root trait affecting the soil detachment, and it estimated the soil detachment capacity well. An equation with few factors was suggested to simulate the soil detachment capacity when the plant root parameters and soil properties were limited.