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Author: search.filters.author.Boldrin, David

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    Seasonal dynamics of root growth and desiccation cracks and their effects on soil hydraulic conductivity
    (2025-04-01)
    Yuliana, Yuliana
    ;
    Apriyono, Arwan
    ;
    Kamchoom, Viroon
    ;
    Boldrin, David
    ;
    Cheng, Qing
    Vegetation significantly influences soil hydraulic conductivity, with the extent of this influence depending on root morphology and density, which vary across different developmental stages of plants. This research investigates the interaction dynamics between plant roots (during both growth and decay) and desiccation cracks, as well as the combined impact of vegetation, cracks, and seasonal variations on soil hydraulic conductivity (K<inf>sat</inf>). Root growth and decay patterns were observed using a minirhizotron, while changes in crack formation were monitored and interpreted using the Crack Intensity Factor (CIF) for both vegetated and bare areas over an eighteen-month period of wetting and drying cycles. K<inf>sat</inf> was analysed based on data from a double-ring test. The findings indicate that the presence of vetiver roots results in a less visible and uneven crack distribution compared to bare soil, with CIF and average crack widths reduced by half. However, cracks reappear during root decay periods. Although cracks were minimised in vegetated soil, K<inf>sat</inf> values increased significantly during dry periods, with a 16-fold rise in the vegetated zone due to root propagation, while the bare zone showed a marginal 5-fold increase. The presence of cracks and roots significantly influences K<inf>sat</inf>, exhibiting distinct hysteresis behaviour in response to drying and wetting cycles.
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    Shearing behaviour of vegetated soils with growing and decaying roots
    (2022-12-01)
    Kamchoom, Viroon
    ;
    Leung, Anthony Kwan
    ;
    Boldrin, David
    ;
    Sakolpanya, Tapakorn
    ;
    Wu, Zhaoyi
    Plant roots affect the soil shear strength, but the temporal dynamics of roots such as growth and decay due to different mortality means have rarely been considered. This study investigates the effects of root growth and decay on the changes in root biomechanical properties and the shearing behaviour of vegetated soils. Columns of compacted soils were grown with a grass species, Cynodon dactylon. The grass was grown for 6 months, followed by burning or herbicide applications to introduce root decay. The top part of each column was used for direct shear tests, whilst the roots collected from the bottom part were used for the measurements of root tensile and chemical properties. The vegetated soils displayed greater shear strength and larger dilatancy, which were attributable to the growth-induced increase in the root cellulose content, and thus the root tensile strength and modulus. Root decay, upon burning or herbicide use, caused significant declines in the root tensile properties, which translated to the reductions in soil dilatancy and soil shear strength lower than those of the fallow soil. Herbicide use introduced a much faster and significant loss of root reinforcement than burning because of the more severe decay and loss of root biomechanical properties.
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    Biomechanical properties of the growing and decaying roots of Cynodon dactylon
    (2022-02-01)
    Kamchoom, Viroon
    ;
    Boldrin, David
    ;
    Leung, Anthony Kwan
    ;
    Sookkrajang, Chanakan
    ;
    Likitlersuang, Suched
    Aim: Root growth and decay may affect root reinforcement to soil erosion and stability. We measured the effects of growth and decay on the tensile strength of Cynodon dactylon roots considering different causes of mortality common to agricultural land conversion (i.e. burning and herbicide application). Method: We applied three treatments to C. dactylon grass: (i) growth duration (60, 120 and 180 days), (ii) decay duration after burning (30, 60, 120, 180 and 360 days) and (iii) decay duration after herbicide application (15, 30 and 60 days). The diameter, tensile strength and cellulose and lignin contents of root samples (n = 303) in different treatments were measured. Results: Tensile strength–diameter relations followed a negative power law regardless of treatment (R<sup>2</sup> > 0.6). The increase in median tensile strength values due to grass growth was consistent with the increase in cellulose and lignin contents. Root decay by herbicide application caused significantly greater and faster reduction in tensile strength than burning treatment because of the faster reduction of cellulose and lignin contents. Conclusion: Root decay due to different causes of plant mortality can increase susceptibility to erosion and slope instability during the conversion of agricultural land. Measures on slope safety and erosion are vital when using herbicides for weed clearance in farmlands due to the faster deterioration of root chemical composition and root tensile strength (compared with burning).