FIGURE 3 - uploaded by Anthony John Miller
Content may be subject to copyright.
Representative raw greyscale X-ray CT images showing soil, root, and pore space after 8 days of growth: (a) Pea in loamy sand soil showing gap formation immediately at the root surface; (b,c) wheat in clay loam soil showing cracks radiating from the root surface; and (d) pea in clay loam soil showing densification of the soil surrounding the root
Source publication
Roots naturally exert axial and radial pressures during growth which alter the structural arrangement of soil at the root‐soil interface. However empirical models suggest soil densificatsion, which can have negative impacts on water and nutrient uptake, occurs at the immediate root surface with decreasing distance from the root. Here we spatially m...
Contexts in source publication
Context 1
... at a higher resolution revealed a clear gap formation around tap and lateral roots in both soil textures (Figure 3), the diameter of which approximately equalled the zones of increased porosity quantified in Figures 1 and 2. Beyond this initial gap formation, changes to porosity at increased distance from the root surface were explained by soil texture and bulk density. ...
Context 2
... observed that roots exhibited a clear strategy where lateral roots explore newly formed fissures, potentially as an energy conservation mechanism. This also accounts for a degree of gap formation immediately around the tap and lateral roots (Figure 3b,c), as the roots often failed to fully fill the pores. The importance of gap formation around growing roots was highlighted by , with the shrinkage of roots responsible for air-filled gaps particularly pronounced around the tap root. ...
Context 3
... was most likely due some combination of both soil and root shrinkage alongside the thigmotropic response of root development. The way in which particles, especially in structure-less samples, are arranged at the root-soil interface has been proposed to account for the zone of higher porosity (Koebernick et al., 2018), and although we cannot discount that this as a contributing factor, it is clear from Figure 3bd where a particulate structure is not observed, that this is unlikely to explain our findings. At greater distances from the root, there was a compacted region (except for Figure 1d), which was due to either (a) a legacy of soil deformation at the root tip or (b) microscale soil shrinkage due to water uptake by the root. ...
Context 4
... was later supported by experimental work using particle image velocimetry in pure sand at a spatial resolution of 0.5 mm ( Vollsnes et al., 2010), where the displacement of sand particles into pores in their immediate vicinity was facilitated by root growth. Our work confirmed the predictions by Dexter (1987) that following root compression of soil to a minimum porosity and an example of this behaviour is seen in Figure 3d. However, we more commonly observed a dual-zone impact of root growth on soil structure in the rhizosphere (Figures 1 and 2), with the first corresponding to the increase in porosity at the immediate root surface to an approximate distance of 50 μm, only observable by high resolution imaging and not previously considered in similar modelling approaches. ...
Context 5
... at a higher resolution revealed a clear gap formation around tap and lateral roots in both soil textures (Figure 3), the diameter of which approximately equalled the zones of increased porosity quantified in Figures 1 and 2. Beyond this initial gap formation, changes to porosity at increased distance from the root surface were explained by soil texture and bulk density. ...
Context 6
... observed that roots exhibited a clear strategy where lateral roots explore newly formed fissures, potentially as an energy conservation mechanism. This also accounts for a degree of gap formation immediately around the tap and lateral roots (Figure 3b,c), as the roots often failed to fully fill the pores. The importance of gap formation around growing roots was highlighted by , with the shrinkage of roots responsible for air-filled gaps particularly pronounced around the tap root. ...
Context 7
... was most likely due some combination of both soil and root shrinkage alongside the thigmotropic response of root development. The way in which particles, especially in structure-less samples, are arranged at the root-soil interface has been proposed to account for the zone of higher porosity (Koebernick et al., 2018), and although we cannot discount that this as a contributing factor, it is clear from Figure 3bd where a particulate structure is not observed, that this is unlikely to explain our findings. At greater distances from the root, there was a compacted region (except for Figure 1d), which was due to either (a) a legacy of soil deformation at the root tip or (b) microscale soil shrinkage due to water uptake by the root. ...
Context 8
... convex hull for wheat: with the segmented root system in yellow and associated zone of influence in red was later supported by experimental work using particle image velocimetry in pure sand at a spatial resolution of 0.5 mm ( Vollsnes et al., 2010), where the displacement of sand particles into pores in their immediate vicinity was facilitated by root growth. Our work confirmed the predictions by Dexter (1987) that following root compression of soil to a minimum porosity and an example of this behaviour is seen in Figure 3d. However, we more commonly observed a dual-zone impact of root growth on soil structure in the rhizosphere (Figures 1 and 2), with the first corresponding to the increase in porosity at the immediate root surface to an approximate distance of 50 μm, only observable by high resolution imaging and not previously considered in similar modelling approaches. ...
Similar publications
Aims
A reliable root architectural model is required to study tree anchorage, including secondary root growth, from seed to the mature stage.
Methods
We calibrated the generic RootTyp model for the seven root types of Pinus pinaster. We determined most parameter distributions from the means and standard deviations of corresponding features in 92 e...
Citations
... In response to the need for green engineering practices to reduce carbon emissions, green and lowcarbon engineering measures such as vegetation reinforcement [3] and bio-cementation reinforcement [4,5] are advocated to mitigate these hazards. Accordingly, the effects of these methods need to be examined to identify their underpinning mechanisms for broader application. ...
Under the influence of climate change, extreme weather events such as rainstorms may induce fluctuations in soil water content above the groundwater level, thereby causing geological disasters (e.g., landslides). To mitigate these hazards, green and low-carbon engineering measures such as vegetation reinforcement and bio-cementation are proposed. This study investigates the micromechanical properties of multiphase geomaterials—unsaturated soil, vegetation-reinforced sand, and bio-cemented sand—utilizing high-resolution computed tomography (CT) scanning technology and associated image analysis techniques. The findings are presented as follows: (1) a 4D examination of the macroscopic and microscopic behaviors of unsaturated granular materials under triaxial loading conditions was conducted using self-designed in situ CT scanning equipment. (2) Triaxial loading alters the distribution of phase interfacial surfaces in unsaturated soil, affecting its overall strength. This loading also increases the anisotropy of the solid skeleton and suction stress. (3) The global saturation of the root–soil complex diminishes with root growth, with pore distribution significantly influencing local saturation. (4) In the unsaturated MICP process, low-saturation conditions are preferable for effective cementation, although the saturation levels should be restricted to 20%. After calcification, the particle contact coordination number increases, maintaining the isotropy in the contact between the soil particles.
... One of the plant adaptations to water deficit conditions is to shed leaves to reduce the respiration rate so that the plant can survive in these conditions. Plants will change the direction of their growth so that the photosynthesis process becomes more efficient, namely by reducing leaf growth and stimulating root growth to absorb water and nutrients [40][41][42]. ...
... The plugins of "Region Growing" and "Draw" in VG Studio Max 3.4 (Volume Graphics GmbH) were interactively used to segment the artificial pores, artificial root-pores, and maize roots (Helliwell et al., 2019). The interaction between roots and artificial pores (or root-pores) was expressed in terms of root utilisation of pores (e.g., the times of pores used by roots). of Ascomycota and Actinobacteria in the artificial rhizosheath, however, was significantly higher than that of the bulk soil, while the proportion of Mortierellomycota, Proteobacteria, Acidobacteria, Verrucomicrobia and Chloroflexi, etc. were significantly lower than that in the bulk soil. ...
Pores and old root‐channels are preferentially used by roots to allow them to penetrate hard soils. However, there are few studies that have accounted for the effects of pore‐rhizosheath on root growth. In this study, we developed an approach by adding the synthetic root exudates using a porous stainless tube with 0.1‐mm micropores through a peristaltic pump to reproduce the rhizosheath around the artificial pore, and investigated the effects of pores with and without rhizosheaths on maize root growth in a dense soil. The results indicated that the artificial rhizosheath was about 2.69 mm wide in the region surrounding the pores. The rhizosheath had a higher content of organic carbon, total nitrogen, and abundance of Actinobacteria than that of the bulk soil. Compared with the artificial macropores, the artificial root‐pores with a rhizosheath increased the opportunities for root utilisation of the pores space, promoting steeper and deeper root growth. It is concluded that the pore‐rhizosheath has a significant impact on root architecture by enhancing root distribution in macropores.
... Decreasing soil porosity toward the root surface has long been postulated in a conceptual model by Dexter (1987) and was more recently directly observed by Aravena et al. (2011) in small soil cylinders filled with soil aggregates. However, Helliwell et al. (2019) reported an increase in porosity at the immediate root surface above the root tip in different soils and for different plant species, indicating the complexity of spatial rearrangement of soil particles due to plant activity. This was confirmed by Koebernick et al. (2019) in a Synchrotron-CT experiment, where the pore space was analysed at a micrometer resolution. ...
... This mucus helps to bind soil particles together, creating small biopores in the soil [64]. These biopores improve the soil's ability to retain water A c c e p t e d m a n u s c r i p t ACCEPTED MANUSCRIPT 3 and nutrients, and they also provide a home for beneficial microorganisms [6,14,16,21,28,59,65]. The presence of biopores can have a significant impact on the rhizosphere, the region of soil directly influenced by the roots of a plant. ...
This study aimed to enhance the understanding of root-soil interaction at a microscale level and its implications for practical land management, ecosystem restoration, and engineered solutions on vegetated slopes. Specifically, the interaction between tall fescue roots and sand was investigated using four-dimensional (4D) CT scanning. The growth process of tall fescue roots in sand was tracked on the 2nd, 4th, 6th, and 8th days after seed transplantation. To accurately segment root-soil CT images and overcome challenges such as the partial volume effect (PVE) and the similarity of root water grayscale in CT images, a semi-automatic segmentation process was employed. The analysis focused on examining the evolution of three-dimensional root parameters throughout the growth process. The findings highlighted the significant influence of initial porosity on tall fescue root development, the global decrease in saturation with root growth, and the predominant impact of pore distribution on local saturation distribution. The study revealed that the root system's influence on saturation, on the eighth day after transplantation, extended up to 800 pixels (8 mm) from the root surface. These results have practical implications for optimizing planting density and providing effective planting strategies for vegetated slope design in engineering applications.
... This might be related to the minimal number of roots that are often present on the weakened surface. The RAR, which measures the average root rate per unit area of soil, has typically been less than 1% (Helliwell et al., 2019). ...
The roots of vetiver grasses can act as a reinforcement and reduce the intensity of slope erosion by protecting the slope from raindrop impact through the anchorage effect and by improving the physio-mechanical behaviour of the soil. This study examined the influence of roots on the shear strength of silty clay soils. Grasses of native species of the Himalayan forest were used as soil reinforcement in the present experimental study. The study concentrates on the shear strength enhancement and improvement in the physical characteristics of the soil-root matrix. Root content has been varied from 0 to 2.5% with an increment of 0.5%. The soil cohesion is found to improve significantly compared to enhancement in the angle of internal friction. The reinforced soil exhibits improved stress-strain behaviour and ductility of soil. These results can serve as a technical basis that can support the utilisation of locally available environmentally friendly grass roots for erosion control and slope stabilisation.
... The physical properties show a dominant silt content of 58.37 ± 2.55%, which can potentially lead to poor soil structure, prone to waterlogging and reduced aeration. The percentages of sand and clay are 6.81 ± 0.24% and 20.35 ± 2.13%, respectively, suggesting a texture that might be susceptible to erosion and compaction, further compromising plant root penetration and water infiltration (Helliwell et al., 2019). Despite these challenges, the soil maintains a low bulk density (0.62 ± 0.02 g/cm 3 ) and a porosity of 37.16 ± 2.89%, implying favorable structure and water-holding capacity but with an underlying risk of waterlogging due to high silt content. ...
Heavy metal contamination from coal mining calls for advanced bioremediation, i.e., using sulfate-reducing bacteria (SRB) technology. Yet, the interaction of SRB with native soil microbiota during metal sequestration, especially in the presence of plants, remains ambiguous. In this study, we assessed the metal sequestration capabilities, ecological network interactions, and enzymatic functions in soils treated with a predominant SRB consortium, mainly Desulfovibrio (14 OTUs, 42.15%) and Desulfobulbus (7 OTUs, 42.27%), alongside Acacia dealbata (AD) and Pisum sativum (PS) plants. The SRB consortium notably enhanced the immobilization of metals such as Zn, Cu, As, and Pb in soil, with the conversion of metals to residual forms rising from 23.47 to 75.98%. Plant inclusion introduced variability, potentially due to changes in root exudates under metal stress. While AD flourished, PS demonstrated significant enhancement in conjunction with SRB, despite initial challenges. Comprehensive microbial analyses revealed the pivotal role of SRB in influencing microbial networking, underpinning critical ecological links. This interplay between plants and SRB not only enhanced microbial diversity but also enriched soil nutrients. Further, enzymatic assessments, highlighting enzymes like NADH:ubiquinone reductase and non-specific serine/threonine protein kinase , reinforced contribution of SRB to energy metabolism and environmental resilience of the entire soil microbial community. Overall, this research underscores the potential of SRB-driven bioremediation in revitalizing soils affected by coal mining.
... Cropping systems influence soil pore characteristics (Helliwell et al., 2019;Lucas et al., 2022b) due in part to differences in root architectures and biomass, quantities and qualities of C inputs, and rhizosphere microbial community composition (Pagliai and De Nobili, 1993;Sprunger et al., 2017;Lucas et al., 2022a). Of particular relevance for microbial activity and, thus, for processing and protection of the newly added C are the pores in the tens to hundreds micrometer size range, which we will refer to here as medium pores. ...
Perennial vegetation with high plant diversity, e.g., restored prairie, is known for stimulation of soil carbon (C) gains, due in part to enhanced formation of pore structure beneficial for long-term C storage. However, the prevalence of this phenomenon across soils of different types remains poorly understood. The aim of the study was to assess the associations between pore structure, soil C, and their differences in monoculture switchgrass and polyculture restored prairie vegetation across a wide range of soils dominating the Upper Midwest of the USA. Six experimental sites were sampled, representing three soil types with texture ranging from sandy to silt loams. The two vegetation systems studied at each site were (i) monoculture switchgrass (Panicum virgatum L.), and (ii) polyculture restored prairie, also containing switchgrass as one of its species. X-ray computed micro-tomography (µCT) was employed to analyze soil pore structure. Structural equation modeling and multiple path analyses were used to assess direct and indirect effects of soil texture and pore characteristics on microbial biomass C (MBC), particulate organic matter (POM), dissolved organic C (DOC), short-term respiration (CO 2), and, ultimately, soil organic C (SOC). Across studied sites, prairie increased fractions of medium (50-150 µm Ø) pores by 11-45 %, SOC by 3-69 %, and MBC by 18-59 % (except for one site). The greater were the prairie-induced increases in the medium pore volumes, the greater were the prairie-induced SOC gains. Greater C losses via CO 2 and DOC contributed to slower C accumulation in the prairie soil. We surmise that the interactive feedback loop relating medium pores and soil C acts across a wide range of soil textures and is an important mechanism through which perennial vegetation with high plant diversity, such as restored prairie, promotes rapid SOC gains.
... Total volumes of soil biopores, i.e., the pores formed by the activity of living organisms such as roots, in Ø <0.2 mm and 0.2-0.5 mm size classes significantly differed among the plant species with different root system characteristics (Lucas, Nguyen, Guber, & Kravchenko, 2022). The differences in pore structure generated by plants with contrasting root systems are expected to be more pronounced in direct vicinity of the roots (Helliwell, Sturrock, Miller, Whalley, & Mooney, 2019), thus, carried later into the properties of the detritusphere. After plant dies, the root residues located in the biopores are decomposed, and the difference in the magnitude of decomposition is likely to be affected by the detritusphere's pore structure. ...
... While the structure of pores within the rhizosphere under different soil texture and contrasting vegetation has been actively explored (Helliwell et al., 2017;Helliwell et al., 2019;Phalempin et al., 2022Phalempin et al., , 2021b, very little information is available on pore structure of detritusphere. For example, Helliwell et al. (2017) observed micro-scale structural changes in pores surrounding growing root systems in uniformly packed soils and found increases in porosity at the interface between roots and soil as roots grow into loamy sand and clay loam soils. ...
Root detritusphere, i.e., the soil in vicinity of decomposing root residues, plays an important role in soil microbial activity and C sequestration. Pore structure (size distributions and connectivity of soil pores) in the detritusphere serves as a major driver for these processes and, in turn, is influenced by physical characteristics of both soil and roots. This study compared pore structure characteristics in root detritusphere of soils of contrasting texture and mineralogy subjected to >6 years of contrasting vegetation: monoculture switchgrass and polyculture prairie systems. Soil samples were collected from five experimental sites in the US Midwest representing three soil types. Soil texture and mineralogy were measured using hydrometer and X-ray powder diffraction, respectively. The intact cores were scanned with X-ray computed micro-tomography to identify visible soil pores, biopores, and particulate organic matter (POM). We specifically focused on pore structure within the detritusphere around the POM of root origin. Results showed that detritusphere of coarser-textured soils, characterized by high sand and quartz contents, had lower porosity in the vicinity of POM compared to finer-textured soils. POM vicinities in finer soils had high proportions of large (>300 μm Ø) pores, and their pores were better connected than in coarser soils. Lower porosity in outer (>1 mm) parts of detritusphere of switchgrass than of prairie suggested soil compaction by roots, and the effect especially pronounced in coarser soils. The results demonstrated that soil texture and mineralogy played a major, while vegetation a more modest, role in defining the pore structure in root detritusphere.
... Its permeable composition and abundant pores facilitate plant growth. When dry, sandy soil develops narrow cracks that benefit crops in regions with erratic rainfall [58,59]. Conversely, clay soil retains water but expands and contracts, stressing plant roots. ...
Biplot analysis has emerged as a crucial statistical method in plant breeding and agricultural research. The objective of this research was to identify the best-performing genotype(s) for the environments in three distinct regions of Nigeria while also examining the characteristics and magnitude of genotype-environment interaction (GEI) effects on the yield of Bambara groundnut (BGN). The study was conducted in Ibadan, Ikenne, and Mokwa, utilizing a sample of 30 accessions. The yield of BGN was found to be significantly affected by accessions, environment, and their interaction through a combined analysis of variance, with a p-value < 0.001. Biplots were utilized to demonstrate the pattern of interaction components, specifically the genotype's main effect and genotype-environment interaction (GEI). The initial two principal components elucidated the complete variance of the GGE model, encompassing both genetic and genotype-by-environment interaction effects (PC1 = 87.81%, PC2 = 12.19%). The accessions that exhibited superior performance in each respective environment, were stable and adaptable in all environments. The accessions that were chosen have been suggested as suitable parental lines for breeding programs aimed at enhancing grain yield in the agro-ecological zones that were evaluated. This study's findings identify BGN accessions with adaptability and stability across selected environments in Nigeria, suggesting specific accessions that can serve as suitable parental lines in breeding programs to enhance grain yield, thereby holding promise for improving food security.
