Willow Roots Research Articles

Phytoremediation potential of poplar and willow species in small scale constructed wetland for boron removal

Boron (B) pollution is an expanding environmental problem throughout the world due to intensive mining practices and extensive usage of B in agricultural chemicals and industrial products in recent years. The purpose of this study was to investigate B removal performance of four poplar and four willow species in small scale Constructed Wetland (CW). Rooted cuttings of tested species were treated with simulated wastewater having five elevated B concentrations (0.5, 5, 10, 20 and 40 ppm). All the tested species could resist up to 20 ppm wastewater B supply and could regrow from their roots in the soil having maximum 15 mg/kg B content. The result of the study indicated that 65% ± 5.3 of B was removed from the wastewater in 5 ppm B treatment while the same efficiency decreased to 45% ± 4.6 at 40 ppm B supply. The average effect of sediment on B removal was found to be approximately 20% for all B treatments while the remaining part of the loaded B was removed from the CW within effluent (35–54%). Therefore, actual effects of plant species on B removal was ranged from 45% to 25% between 5 and 40 ppm B treatments. Mass B removal within plant body (phytextraction) comprised the 13-10% of total loaded B in CW while the remaining part of the loaded B (31-15%) was stabilized into the sediment with the effects of poplar and willow roots. These results presented clear understanding of effective B purification mechanisms in CWs. Boron phytextraction capacity of a plant species was less effective than its phytstabilization efficiency which increase filtering capacity of the sediment and stabilization of more B around the rhizosphere. In terms of their B removal ability, P.nigra and S.anatolica had the highest B removal capacities with phytextraction (20-11%) while S.alba, P.alba and S.babylonica had more phytstabilizaiton performance (40-15%) in CW. Disposal of B loaded plant material create another environmental costs for CW applications. Therefore, B loaded wood and leaf tissues were mixed and used for production of wooden panels in the study. Then a combustion test was applied on these panels to test their fire resistance. The results of the tests revealed much higher burning tolerance of the B loaded panels (5–20%) compared to controls. Annual harvesting, fast growing and deep rooting ability of the poplar and willow species with their high phytstabilization and phytextraction efficiencies make these species excellent tools to remove B from the polluted waters. Utilization of these species for B removal in large scale CWs is quite possible which should be also investigated in further studies.

Above- and Belowground Development of a Fast-Growing Willow Planted in Acid-Generating Mine Technosol.

Surface metal mining produces large volumes of waste rocks. If they contain sulfide minerals, these rocks can generate a flow of acidic water from the mining site, known as acid mine drainage (AMD), which increases trace metals availability for plant roots. Adequate root development is crucial to decreasing planting stress and improving phytoremediation with woody species. However, techniques to improve revegetation success rarely take into account root development. An experiment was conducted at a gold mine in Quebec, Canada, to evaluate the establishment ability over 3 yr of a fast-growing willow ( Sx64) planted in acid-generating waste rocks. The main objective was to study root development in the soil profile and trace element accumulation in leaves among substrates varying in thickness (0, 20, and 40 cm of soil) and composition (organic carbon [OC] and alkaline AMD treatment sludge). Trees directly planted in waste rocks survived well (69%) but had the lowest productivity (lowest growth in height and diameter, aerial biomass, total leaf area, and root-system size). By contrast, the treatment richer in OC showed the greatest aerial biomass and total leaf area the first year; the thicker treatment resulted in the greatest growth in height and diameter, aboveground biomass, and root-system size in both the first and third years. Willow root development was restricted to soil layers during the first year, but this restriction was overcome in the third year after planting. Willow accumulation factors in leaves were below one for all investigated trace metals except for zinc (Zn), cadmium (Cd), and strontium. For Cd and Zn, concentrations increased with time in willow foliage, decreasing the potential of this willow species use for phytostabilization, despite its ability to rapidly develop extensive root systems in the mine Technosol.

The potential of the decay fungus Chondrostereum purpureum in the biocontrol of broadleaved tree species

Abstract The ability of the decay fungus Chondrostereum purpureum to grow within birch (Betula pendula and Betula pubescens), aspen (Populus tremula), rowan (Sorbus aucuparia) and willow (Salix caprea) stumps or root systems is unknown, although such information would be crucial in understanding its impact on the vegetative growth of broadleaved trees, their ecology and potential biocontrol. Saplings of these tree species were cut and inoculated with the fungus. After 3 months, 47, 14, 0 and 0% of birch, aspen, rowan and willow stumps, respectively, were dead, and C. purpureum was frequently present within the stumps of all species. In more than half of the birch stumps investigated, the fungus had penetrated into the roots unlike in the other tree species. Our results indicate that C. purpureum can utilize the woody material of birch better than that of other species, and that penetration into the roots is needed to kill the host.

Can liming change root anatomy, biomass allocation and trace element distribution among plant parts of Salix × smithiana in trace element-polluted soils?

Willows (Salix spp.) are considered to be effective for the phytoremediation of trace elements from contaminated soils, but their efficiency is limited in heavily polluted soils because of poor growth. Liming can be a desirable measure to decrease the plant availability of elements, resulting in improved plant development. Notably, large root area and maximum soil penetration are basic parameters that improve the efficiency of phytoremediation. The impact of soil chemical properties on willow root anatomy and the distribution of trace elements below-ground have rarely been studied. The effect of liming on root parameters, biomass allocation and trace element distribution in non-harvestable (coarse roots, fine roots, stumps) and harvestable plant parts (twigs and leaves) of Salix × smithiana was assessed at the end of a 4-year pot experiment with two trace element-polluted soils that differed in terms of soil pH. Stump biomass predominated in weakly acidic soil. In neutral soil, the majority of biomass was located in fine roots and stumps; the difference from other plant parts was minor. Trace elements were the most concentrated in fine roots. Translocation to above-ground biomass increased as follows: Pb < As < Zn~Cd. In contrast to Cd and Zn, great differences in As and Pb mobility in plants were recorded after measurements of individual below-ground biomass (stumps < coarse roots < fine roots). Lime application decreased the concentrations of mobile Cd and Zn and related levels in plants, improved biomass production and root parameters and increased the removal of all trace elements in weakly acidic soil. None or minimum differences in the monitored parameters were recorded for dolomite treatments in both soils. The dose and source of liming had crucial effects on root anatomy. Growing willows in limed trace element-polluted soils is a suitable measure for combination of two remediation strategies, i.e. phytoextraction of Cd and Zn and assisted phytostabilization of As and Pb.

Nesting Success of MallardAnas platyrhynchosat Kashmir Lakes, India, is Associated with Nest Location

Nesting success of Mallard Anas platyrhynchos was evaluated at Haigam, Hokarsar and Shalabug lakes in Kashmir in 2012 and 2013. Nests were located, tagged and monitored until the clutch hatched. Nest location, nest volume and height above water/ground measured, and threats were all noted. A total of 95 nests with 556 eggs within tree holes, willow root mats or reed beds were monitored. Nests in which at least one egg hatched were deemed successful. A logistic regression was used to identify variables associated with nesting success over two years. Nesting success was 53% and hatching success 64%. Nesting success was significantly higher within tree holes due to lower risk from flooding and human disturbance. About 27% of nests were affected by human harvesting and 16% by flooding.

Transplanting Soil Microbiomes Leads to Lasting Effects on Willow Growth, but not on the Rhizosphere Microbiome.

Plants interact closely with microbes, which are partly responsible for plant growth, health, and adaptation to stressful environments. Engineering the plant-associated microbiome could improve plant survival and performance in stressful environments such as contaminated soils. Here, willow cuttings were planted into highly petroleum-contaminated soils that had been gamma-irradiated and subjected to one of four treatments: inoculation with rhizosphere soil from a willow that grew well (LA) or sub-optimally (SM) in highly contaminated soils or with bulk soil in which the planted willow had died (DE) or no inoculation (CO). Samples were taken from the starting inoculum, at the beginning of the experiment (T0) and after 100 days of growth (TF). Short hypervariable regions of archaeal/bacterial 16S rRNA genes and the fungal ITS region were amplified from soil DNA extracts and sequenced on the Illumina MiSeq. Willow growth was monitored throughout the experiment, and plant biomass was measured at TF. CO willows were significantly smaller throughout the experiment, while DE willows were the largest at TF. Microbiomes of different treatments were divergent at T0, but for most samples, had converged on highly similar communities by TF. Willow biomass was more strongly linked to overall microbial community structure at T0 than to microbial community structure at TF, and the relative abundance of many genera at T0 was significantly correlated to final willow root and shoot biomass. Although microbial communities had mostly converged at TF, lasting differences in willow growth were observed, probably linked to differences in T0 microbial communities.

Determining an Optimum Tree Species for the Phytoremediation of Cumene and 4-Cumylphenol in Groundwater

Cumene and 4-cumylphenol are the primary constituents of concern in a groundwater plume at a chemical facility located in Plaquemine, Louisiana. Phytoremediation, a method that uses plants to remove contaminants from water and soil, was posed as a solution to removing the constituents of concern and creating hydraulic control of the plume. Five tree species, eastern redcedar, bald cypress, black willow, eastern cottonwood, and water oak, were chosen as potential remediators. Eastern redcedar and water oak did not tolerate the saline, contaminated water. Bald cypress, black willow, and eastern cottonwood trees were irrigated with deionized water, deionized water containing 0.5 mg·L−1 (0.5 ppm) cumene and 1 mg·L−1 (1 ppm) 4-cumylphenol as the low concentration, or deionized water containing 1 mg·L−1 (1 ppm) cumene and 4 mg·L−1 (4 ppm) 4-cumylphenol referred to as the high concentration. Both bald cypress and black willow were the best tree species for remediation of the groundwater as they were able to sequester the constituents of concern in their lower root tissue. Mean concentration of 4-cumylphenol detected in bald cypress roots at the end of the study were 1.72 mg·kg−1 in the low concentration water treatment and 1.50 mg·kg−1 in the high concentration water treatment. Mean concentration of 4-cumylphenol detected in black willow roots at the end of the study were 16.58 mg·kg−1 in the low concentration water treatment and 25.65 mg·kg−1 in the high concentration water treatment. Bald cypress was ultimately chosen for full scale planting in the fall of 2008.

Willow Root Development and Morphology Changes Under Different Irrigation and Fertilization Regimes in a Vegetation Filter

Determining the appropriate wastewater dose to supply nutrients while avoiding overirrigation is essential for achieving more balanced above- and belowground development of the plants, thereby ensuring high filtering functionality of a willow vegetation filter system. Aboveground biomass and root development of a 3-year-old willow vegetation filter in response to three increasing doses of secondary-treated urban wastewater under both fertilized and unfertilized conditions were evaluated. Fine, coarse and total root biomass, fine root length density (FRLD), specific fine root length (SFRL) and specific root area (SRA) were assessed in soil core samples collected at four different depths (0–20, 20–40, 40–60 and 60–80 cm) in all treatments. While aboveground biomass increased as wastewater amounts and fertilization increased (from 23.89 Mg ha−1 in non-irrigated condition to 47.07 Mg ha−1 in the highest wastewater dose, from 31.5 Mg ha−1 in unfertilized plots to 40.1 Mg ha−1 in the fertilized), total and fine root biomass decreased when willow was irrigated with the highest wastewater dose (i.e. total root biomass is 2.54 Mg ha−1 in non-irrigated condition—1.36 Mg ha−1 in the highest wastewater dose). The root biomass did not follow the same development pattern, and a significant decrease in fine root biomass was observed when the highest irrigation dose was applied. In these circumstances, we believe that the supply in water and nutrient is sufficient to the development of the willows which react by diminishing the amount of roots proportionally to the aboveground parts. This may lead to a higher transpiration rate and allow willows to avoid a surplus of water in the soil.

Host genotype and health status influence on the composition of the arbuscular mycorrhizal fungi in Salix bioenergy plantations

In agricultural production systems, fast-growing trees such as willow (Salix spp.) have gained popularity as a sustainable source of bioenergy and bioproducts. Among the diverse fungi in symbiosis with roots of willow, arbuscular mycorrhizal fungi (AMF) may play a crucial role in the establishment and growth of willow in short rotation intensive cultures (SRIC). An approach based on the denaturing gradient gel electrophoresis (DGGE) technique was developed to study AMF communities and their effect on Salix growth and disease resistance in SRIC. The DGGE patterns and the sequences of major DGGE bands obtained with the large subunit rDNA primer set (LSU) showed an important shift in diversity of AMF communities in healthy compared to diseased plants. The AMF communities consisted of Glomus sp., G. clarum, G. claroideum, G. mosseae, G. geosporum-G. cf. diaphanum complex, Rhizophagus irregularis (syn. Glomus irregulare/G. intraradices) and Glo-S, a possible undescribed glomeromycete species. The structure of AMF communities, as well as possible role of each AMF taxon, appeared to be dependent upon the cultivar to which they associate. This calls attention to consider the ecological implications, for biomass production, of the specificity of the association between particular willow cultivars and AMF.

Cadmium adsorption by willow root: the role of cell walls and their subfractions

Plant cell walls may play an important role in the uptake and accumulation of heavy metals. This study was undertaken to obtain a better understanding of the role of the root cell walls (RCW) and their subfractions on adsorption of cadmium (Cd) in a promising woody phytoremediation species, Salix jiangsuensis J172. In order to examine how Cd binding was affected by pectin and hemicellulose, RCW were isolated and sequentially fractioned by removing pectin (RCW1), partial removal of hemicellulose (RCW2), and complete removal of hemicellulose (RCW3). The RCW and fractions were characterized by Fourier transform infrared spectroscopy, which suggested decomposition of hemicellulose and a decline in nitrogen content following cell wall isolation and fractionation. The adsorption affinity of Cd increased gradually following the sequential extraction of root cells, suggesting that hemicellulose negatively impacted Cd adsorption, while pectin and cellulose enhanced Cd adsorption. Cd adsorption dynamics and isotherms could be best described by the pseudo-second-order (R>0.99) and Freundlich (R>0.97) models, respectively. Thermodynamic properties (∆G, ∆H, and ∆S), determined using the van't Hoff equation, indicated that while Cd adsorption was endothermic, and spontaneous for RCW2 and RCW3, adsorption was not spontaneous for the root, RCW, and RCW1. The results provide evidence for the importance of the root cell walls in the adsorption of Cd by willow roots.

A novel pre-treatment for rapidly separating willow roots from high clay content soil

Numerous studies have examined the root dynamics of willow biomass energy crops growing on medium to light-textured soils, using either soil coring, minirhizotron techniques, or a combination thereof. However, neither approach is well suited for studying roots in expansive high clay content soil. Our objective was to test the efficacy of a novel inexpensive root washing pre-treatment, using baking soda (NaHCO3), for facilitating the separation of willow roots from a Vertisol (70% clay). Soil cores were collected from within a willow variety trial plot of Tully Champion (Salix viminalis × Salix miyabeana) and were either conventionally washed (i.e., no pre-treatment) or washed following a pre-treatment consisting of shaking the sample for 15 min with either deionized water or 1.2 mol dm−3 NaHCO3. Measurement variables included washing duration, water usage, and recovery of fine (<2 mm) and coarse roots. The ranking of washing duration and water usage was NaHCO3 pre-treatment < deionized water pre-treatment < conventional washing. Compared to conventional washing, the NaHCO3 pre-treatment reduced the washing duration and water usage by 45 and 61%, respectively, while increasing the fine root recovery by 26%. There was no significant difference (P > 0.05) in the fine root recovery between the deionized water and NaHCO3 pre-treatments or the coarse root recovery among the three washing methods. Developing a quicker technique of separating willow roots from high clay content soil, which conserves water and increases fine root recovery, should promote further investigations of root growth dynamics within this traditionally difficult soil type.

Eriosomatine aphids (Hemiptera: Aphididae: Eriosomatinae) associated with moss and roots of conifer and willow in forests of the Pacific Northwest of North America

AbstractApterous adult morphs of eriosomatine aphids associated with moss (Bryophyta) and/or roots of conifer (Pinaceae) or willow (SalixLinnaeus (Salicaceae)) in forests of the North American Pacific Northwest including Alaska are described, illustrated, and keyed. In total, seven species (Clydesmithia canadensisDanielsson,Melaphis rhois(Fitch) (moss only feeder),Pachypappa rosettei(Maxson),Pachypappa sacculi(Gillette),Prociphilus americanus(Walker) (fir root only feeder),Prociphilus xylostei(De Geer), andThecabius populimonilis(Riley)) are characterised from their secondary host habitats. Secondary host forms ofC. canadensisandT.populimonilisare described for the first time. The morphotypes from the secondary hosts were confirmed through deoxyribonucleic acid sequence matching with those from the primary hosts.

Uptake of cadmium from hydroponic solutions by willows (Salix spp.) seedlings

Willow ( Salix sp.) has large biomass production and high resistance to environmental stress. As an important multipurpose tree species in afforestation, it has been proved to be effective in the uptake and accumulation of metals from contaminated waters and soils. Suliu172 ( Salix × jiangsuensis 'J172'), Hanliu ( Salix matsudana ), Weishanhu ( Salix integra 'Weishanhu') and Yizhibi (S. integra 'Yizhibi') were chosen as model plants to evaluate their potential for uptake of cadmium from hydroponic culture and relative uptake mechanism. Cadmium uptake showed a linear increase in the short time course, and a nonlinear and slow increase in the long time course. After one week cultivation, cadmium accumulation in different parts of willows generally followed the order of root > stem > leaf. Cadmium influx in willow roots increased with the increase of cadmium concentration in hydroponic solutions. A modified Michaelis-Menten equation was employed to describe the concentration-dependent kinetics of cadmium uptake through the roots. Cadmium influx could be resolved into linear and saturable components under concentration–dependent kinetics. The saturable component followed Michaelis–Menten kinetics, which indicated that cadmium uptake across the plasma membrane was transporter–mediated. The uptake capacity (V max /K m ) jointly decided by the V max and K m followed descending order of Hanliu > Weishanhu ≈ Yizhibi > Suliu172, indicating that their inherent potential of cadmium uptake reduced in turn. Low temperature and metabolic inhibitor inhibited the apparent uptake of cadmium in willow. Both active absorption and passive absorption occurred in the cadmium uptake by willow roots. Key words : Cadmium, willow, uptake kinetics.

Spatial distribution of arsenic and heavy metals in willow roots from a contaminated floodplain soil measured by X-ray fluorescence spectroscopy

Under changing redox conditions some plants create plaques at their root surface, which may affect the mobility and uptake of As and heavy metals but it is unknown to what extent this also holds true for willows in contaminated floodplain soils. Therefore, willow roots were sampled from a phytoremediation trial in the contaminated floodplain of the river Elbe (Germany), cryofixed, freeze-dried, and cross sections were mapped for the distribution of As, Ca, Cu, Fe, K, Mn, Ni, S and Zn by synchrotron based X-ray fluorescence spectroscopy. The elements Ca, Cu, Ni, S and Zn were concentrated in the aerenchymatic tissue, and not associated with Fe and Mn. Mixed Fe–Mn plaques covered the surface of the willow roots and As was accumulated in these plaques. The observed association pattern between As and Fe was explained by the different sorption/desorption properties of As(III) and As(V). The Cu and Zn intensities were not associated with the intensity of Fe in the plaque, which seems to be a willow-specific difference compared to other wetland plants. These results suggested that willows are especially suited to stabilize low-phytoextractable elements like Cu and As in their roots and rhizosphere. Thus, short rotation coppicing of willows may be a practical approach to mitigate the adverse effects of floodplain soil contamination.

Impact of Exotic Willow Roots (Salix spp.) as Habitat for Aquatic Invertebrate Communities in South Australian Stream

Impact of Exotic Willow Roots (Salix spp.) as Habitat for Aquatic Invertebrate Communities in South Australian Stream

Assessing the potential for rhizoremediation of PCB contaminated soils in northern regions using native tree species

Rhizosphere bioremediation of polychlorinated biphenyls (PCBs) offers a potentially inexpensive approach to remediating contaminated soils that is particularly attractive in remote regions including the Arctic. We assessed the abilities of two tree species native to Alaska, Salix alaxensis (felt-leaf willow) and Picea glauca (white spruce), to promote microbial biodegradation of PCBs via the release of phytochemicals upon fine root death. Crushed fine roots, biphenyl (PCB analogue) or salicylate (willow secondary compound) were added to microcosms containing soil spiked with PCBs and resultant PCB disappearance, soil toxicity and microbial community changes were examined. After 180 d, soil treated with willow root crushates showed a significantly greater PCB loss than untreated soils for some PCB congeners, including the toxic congeners, PCB 77, 105 and 169, and showed a similar PCB loss pattern (in both extent of degradation and congeners degraded) to biphenyl-treated microcosms. Neither P. glauca (white spruce) roots nor salicylate enhanced PCB loss, indicating that biostimulation is plant species specific and was not mediated by salicylate. Soil toxicity assessed using the Microtox bioassay indicated that the willow treatment resulted in a less toxic soil environment. Molecular microbial community analyses indicated that biphenyl and salicylate promoted shifts in microbial community structure and composition that differed distinctly from each other and from the crushed root treatments. The biphenyl utilizing bacterium, Cupriavidus spp. was isolated from the soil. The findings suggest that S. alaxensis may be an effective plant for rhizoremediation by altering microbial community structure, enhancing the loss of some PCB congeners and reducing the toxicity of the soil environment.

Oxygen transfer capacity of willow (Salix viminalis L.)

Willow Salix viminalis L. supplies oxygen into the subsurface environment. Laboratory experiments determined the willow Oxygen Transfer Capacity and its dependence on total leaf area and root wet mass. It was shown, that oxygen is released by roots under light conditions, and the rate of oxygen supplymay be greater than the rate of consumption due to respiration of roots. The mean OTC level was 195.7 [gO 2 . m −3. h −1. kg rwm −1 ]. Nonlinear relationship between OTC and both total leaf area and root wet mass was found, and confirmed by high determination coefficient (R 2 ) values: 0.912 and 0.936. ► We showed that willow – S. viminalis L. releases oxygen into the root zone in a laboratory model system. ► We determined a value for the rate of oxygen release by willow roots (Oxygen Transfer Capacity) in relation to root mass and total leaf area. ► These results may have importance to willow crop plantations dedicated to organic soil (sewage sludge), constructed wetlands, and closed landfills.

Spatial variation of dissolved gas concentrations in a willow vegetation filter treating landfill leachate

Membrane inlet mass spectrometry (MIMS) was used to monitor continuously and simultaneously the concentrations of dissolved gases (O 2, CO 2, CH 4) within the treatment bed of a willow vegetation filter treating leachate at a landfill site in mid Wales. The distribution of dissolved gasses within the bed was shown to be highly heterogeneous at the small spatial scale with considerable variation between vertical profiles measured simultaneously at different locations. In general, aerobic conditions were observed above the water table with reduced levels of oxygen and increasing levels of carbon dioxide and methane below it. Distinct pockets of oxygen (up to 200 μM) were observed in anaerobic zones and pockets of reduced oxygen and elevated carbon dioxide were observed in the aerobic zone. Pockets of methane were observed in some profiles coexisting with up to 200 μM oxygen at 5 cm depth. These observations confirm the hypothesis that micro-sites exists within the soil/root matrix where aerobic organic matter decomposition and anaerobic processes such as methanogenesis can occur in relatively close proximity to each other. We hypothesise that the distribution of dissolved gases is determined by rapid diffusion of air maintaining aerobic conditions above the water table, removal of oxygen by microbial processes creating anaerobic conditions below the water table and the distribution of willow roots in the soil which create local aerobic zones by oxygen release.

Diurnal cycling of dissolved gas concentrations in a willow vegetation filter treating landfill leachate

Membrane inlet mass spectrometry (MIMS) was used to monitor continuously and simultaneously the concentrations of dissolved gases (O 2, CO 2, CH 4), in the willow root zone at the laboratory scale, and within the treatment bed of a willow vegetation filter treating leachate at a landfill site in mid Wales. These results demonstrate that willows are able to release oxygen into the root zone which accumulates during daylight. Diurnal cycles of oxygen, carbon dioxide, and methane were observed, whereby CO 2 and CH 4 varied reciprocally in relation to O 2. The intensity of these cycles appeared to be related to light intensity and temperature. Oxygen was shown to fluctuate between completely anaerobic and fully aerated (300 μM), between day and night in sunny conditions.

Resistance of simple plant root systems to uplift loads

Plant root systems frequently permeate both natural and engineered soil slopes, influencing slope stability via mechanical reinforcement and soil drying. These root systems are often loaded by external forces during slope movements and when plant stems are subject to animal foraging or wind gusts. A series of physical model tests were conducted to examine how root geometries, root properties, and soil effective stress states affect the pullout capacity of simple unbranched model roots. Lengths of wood, rubber, and real roots were pulled from dry and partially saturated sand. The tests revealed the importance of the root to soil stiffness ratio during progressive failure, the mechanical properties of soil (and interfaces) at low effective stresses, the root diameter, and the tortuosity of the root material. Scaling issues due to shear banding are more important, and effective stresses under wet conditions are smaller than in conventional geotechnical practice because roots have a relatively small diameter (typically 10−4–10−1 m) and are at shallow depth (typically 0–2 m). After careful consideration of these effects, predictions were made for the pullout capacity of small root sections based on material data for willow roots (Salix viminalis) in sand.