Dataset Information

Effects of root spatial distribution on the elastic-plastic properties of soil-root blocks.

ABSTRACT: Plant roots significantly influence soil properties, especially in soil beyond the limited area surrounding the main root stem. Some bias results may be generated if plastic properties of soil are merely used in evaluating slope stability without considering the effects of plant roots. In this research, effects of root spatial distribution on the elastic-plastic characteristics of soil-root blocks were examined. Triaxial tests and the Duncan-Chang model were used to analyze the correlation between root spatial characteristics and soil elastic-plastic properties. Safety factors of vegetated slopes were calculated to investigate the effect of roots on slope stability. The limit stress of remoulded soil was 103.52% to 231.61% greater than undisturbed soil in shallow soil layers. Increased root quantity led to an increased the failure ratio of soil bulk and the initial tangent modulus increased with root diameter. When calculating the safety factor of vegetated slopes, soil indexes for soil beyond the small cylinder surrounding the main stem should be properly considered to avoid safety factor overestimation.

SUBMITTER: Li Y

PROVIDER: S-EPMC5429779 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Effects of root spatial distribution on the elastic-plastic properties of soil-root blocks.

Li Yunpeng Y Wang Yunqi Y Wang Yujie Y Ma Chao C

Scientific reports 20170411 1

Plant roots significantly influence soil properties, especially in soil beyond the limited area surrounding the main root stem. Some bias results may be generated if plastic properties of soil are merely used in evaluating slope stability without considering the effects of plant roots. In this research, effects of root spatial distribution on the elastic-plastic characteristics of soil-root blocks were examined. Triaxial tests and the Duncan-Chang model were used to analyze the correlation betwe ...[more]

PMID: 28400584

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Project description:Pore structure is a key determinant of soil functioning, and both root growth and activity of soil fauna are modified by and interact with pore structure in multiple ways. Cover cropping is a rapidly growing popular strategy for improving agricultural sustainability, including improvements in pore structure. However, since cover crop species encompass a variety of contrasting root architectures, they can have disparate effects on formation of soil pores and their characteristics, thus on the pore structure formation. Moreover, utilization of the existing pore systems and its modification by new root growth, in conjunction with soil fauna activity, can also vary by cover crop species, affecting the dynamics of biopores (creation and demolition). The objectives of this study were (i) to quantify the influence of 5 cover crop species on formation and size distribution of soil macropores (>36 μm Ø); (ii) to explore the changes in the originally developed pore architecture after an additional season of cover crop growth; and (iii) to assess the relative contributions of plant roots and soil fauna to fate and modifications of biopores. Intact soil cores were taken from 5 to 10 cm depth after one season of cover crop growth, followed by X-ray computed micro-tomography (CT) characterization, and then, the cores were reburied for a second root growing period of cover crops to explore subsequent changes in pore characteristics with the second CT scanning. Our data suggest that interactions of soil fauna and roots with pore structure changed over time. While in the first season, large biopores were created at the expense of small pores, in the second year these biopores were reused or destroyed by the creation of new ones through earthworm activities and large root growth. In addition, the creation of large biopores (>0.5 mm) increased total macroporosity. During the second root growing period, these large sized macropores, however, are reduced in size again through the action of soil fauna smaller than earthworms, suggesting a highly dynamic equilibrium. Different effects of cover crops on pore structure mainly arise from their differences in root volume, mean diameter as well as their reuse of existing macropores.

Project description:The fluctuation of Meloidogyne population density and the percentage of fungal egg parasitism were determined from July 2011 to July 2013 in two commercial organic vegetable production sites (M10.23 and M10.55) in plastic greenhouses, located in northeastern Spain, in order to know the level of soil suppressiveness. Fungal parasites were identified by molecular methods. In parallel, pot tests characterized the level of soil suppressiveness and the fungal species growing from the eggs. In addition, the egg parasitic ability of 10 fungal isolates per site was also assessed. The genetic profiles of fungal and bacterial populations from M10.23 and M10.55 soils were obtained by Denaturing Gradient Gel Electrophoresis (DGGE), and compared with a non-suppressive soil (M10.33). In M10.23, Meloidogyne population in soil decreased progressively throughout the rotation zucchini, tomato, and radish or spinach. The percentage of egg parasitism was 54.7% in zucchini crop, the only one in which eggs were detected. Pochonia chlamydosporia was the only fungal species isolated. In M10.55, nematode densities peaked at the end of the spring-summer crops (tomato, zucchini, and cucumber), but disease severity was lower than expected (0.2-6.3). The percentage of fungal egg parasitism ranged from 3 to 84.5% in these crops. The results in pot tests confirmed the suppressiveness of the M10.23 and M10.55 soils against Meloidogyne. The number of eggs per plant and the reproduction factor of the population were reduced (P < 0.05) in both non-sterilized soils compared to the sterilized ones after one nematode generation. P. chlamydosporia was the only fungus isolated from Meloidogyne eggs. In in vitro tests, P. chlamydosporia isolates were able to parasitize Meloidogyne eggs from 50 to 97% irrespective of the site. DGGE fingerprints revealed a high diversity in the microbial populations analyzed. Furthermore, both bacterial and fungal genetic patterns differentiated suppressive from non-suppressive soils, but the former showed a higher degree of similarity between both suppressive soils than the later.

Dataset Information

Effects of root spatial distribution on the elastic-plastic properties of soil-root blocks.

Publications

Effects of root spatial distribution on the elastic-plastic properties of soil-root blocks.

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