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Compared to surface application, manure subsurface injection reduces surface runoff of nutrients, antibiotic resistant microorganisms, and emerging contaminants. Less is known regarding the impact of both manure application methods on surface transport of antibiotic resistance genes (ARGs) in manure-amended fields. We applied liquid dairy manure to field plots by surface application and subsurface injection and simulated rainfall on the first or seventh day following application. The ARG richness, relative abundance (normalized to 16s rRNA), and ARG profiles in soil and surface runoff were monitored using shotgun metagenomic sequencing. Within 1 day of manure application, compared to unamended soils, soils treated with manure had 32.5-70.5% greater ARG richness and higher relative abundances of sulfonamide (6.5-129%) and tetracycline (752-3766%) resistance genes (

The hydrological response of steep slopes catchments is strongly conditioned by the connectivity of subsurface preferential flows. The objective of this research is to investigate the role played by stemflow infiltration in subsurface water flow dynamics, focusing on a forested hillslope located in an Aleppo pine Mediterranean forest (Pinus halepensis, Mill.) located at Sierra Calderona, Valencia province, Spain. We combined stemflow artificial experiments with ground-penetrating radar (GPR) techniques as a non-invasive method to investigate stemflow-induced preferential flow paths activated by different trees and the related hydrological connectivity at the hillslope scale. Our observations allowed us to identify different dynamics associated with the initiation of stemflow and then lateral preferential flow, including the activation of connected preferential flow paths in soils that received stemflow water from different trees. These observations provided empirical evidence of the role of stemflow in the formation of lateral preferential flow networks. Our measurements allow estimations of flow velocities and new insight on the magnitude of stem-induced lateral preferential flow paths. The applied protocol offers a simple, repeatable and non-invasive way to conceptualize hillslope responses to rainstorms.

21 Pags.- 8 Figs.- 2 Tabls. © Author(s) 2023. This work is distributed under the Creative Commons Attribution 4.0 License., Sorptivity is one of the most important parameters for the quantification of water infiltration into soils. Parlange (1975) proposed a specific formulation to derive sorptivity as a function of the soil water retention and hydraulic conductivity functions, as well as initial and final soil water contents. However, this formulation requires the integration of a function involving hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this study, we propose a mixed formulation that scales sorptivity and splits the integrals into two parts: the first term involves the scaled degree of saturation, while the second involves the scaled water pressure head. The new mixed formulation is shown to be robust and well-suited to any type of hydraulic function – even with infinite hydraulic diffusivity or positive air-entry water pressure heads – and any boundary condition, including infinite initial water pressure head. Lastly, we show the benefits of using the proposed formulation for modeling water into soil with analytical models that use sorptivity., This work was performed within the INFILTRON project supported by the French National Research Agency. This research has been supported by the Agence Nationale de la Recherche (grant no. ANR-17-CE04-010).

Peatland drainage may degrade system resilience to high intensity, soil-consuming fires. Peat soil fires are unique in that they can smoulder vertically through the soil column, with a multitude of consequences including large carbon emissions, altered hydrology, and dramatic shifts in vegetation communities. In this work we developed and verified a new method to model peat burn depths with readily available water level and peat hydraulic property data at the Great Dismal Swamp National Wildlife Refuge (VA and NC, USA). To model peat burn depths across 11 sites in the Great Dismal Swamp National Wildlife Refuge we combined water table time series data and soil moisture release curves, developed at multiple depths, with moisture-to-ignition thresholds. A subset of the results from this empirical modelling approach of peat burn depth severity were compared against those made using a mechanistic model of soil moisture, HYDRUS 1-D. By comparing modelled burn depth potentials between these two approaches for a range of peats, we confirmed that our simpler, water table-based approach had similar performance to HYDRUS 1-D in drained and degraded peats, like those found in the Great Dismal Swamp National Wildlife Refuge. A comparative analysis of modelled burn depths across our study site found that water table position and peat water holding capacity were the key governing controls on burn depth potential. Our findings suggest that drainage weakens both short- and long-term controls on peat burn depths by reducing soil moisture and by decreasing peat water holding capacity. This new approach offers land managers with an additional tool for assessing risk while offering insight into the drivers of peatland wildfire severity. Published version Public domain – authored by a U.S. government employee

11 Pags.- 5 Figs.- 4 Tabls. © 2022 Elsevier B.V. This is an open access article under the CC BY-NC-ND license., Modeling infiltration in water-repellent soils is difficult, as the underlying processes remain poorly quantified. However, recent work has adapted the Beerkan Soil Transfer Parameter (BEST) algorithm to include an exponential correction term for characterizing these types of soils. The original BEST-WR (WR = Water Repellent) method used a two-term approximate expansion of the Haverkamp quasi-exact implicit model. However, the BEST-WR method can have considerable inaccuracy, particularly as the time of infiltration and the soil water repellency increase. Here, we extended the BEST-WR model by adapting a three-term approximation of the Haverkamp quasi-exact implicit model to water-repellent soils. We then tested the new method using analytical data. For highly water-repellent soils, the proposed method had better performance when estimating soil sorptivity (S) and soil saturated conductivity (Ks), with respective errors of less than 1.5 % and 8 %, compared to relative errors of more than 10 % and 30 % with the two-term BEST-WR method. We also tested both approaches with experimental data. The two methods provided similar estimates for hydraulic parameters, with linear correlations between methods of R2 = 0.84 for S and R2 = 0.88 for Ks. Initial infiltration was not well modeled by either the two-term or three-term model for 33 tests, thus revealing limitations in the applied exponential model that we used to account for soil repellency. Nonetheless, the proposed three-term expression provided better fits than the two-term model for most of the infiltration runs, meaning that this new approach is more robust when modeling infiltration processes in water-repellent soils., This work was supported through the European Regional Development Fund (ERDF) and the Italian Ministry of Education, University and Research (MIUR) through the “Programma Operativo Nazionale (PON) Ricerca e Innovazione 2014-2020“ (Linea 1 - Mobilità dei ricercatori, AIM1853149, CUP: J54I18000120001), and the GASPAM project ”Gestione Agronomica Sostenibile dei Pascoli Arborati Mediterranei“, funded by Regione Sardegna (L. 7/2007, 2019-21).

Methods to measure shrinkage curves typically either disturb natural aggregate structure or include difficult or slow volume measurement techniques. Additionally, most shrinkage curves are obtained by serial measurement of a few samples. We obtained shrinkage curves by collecting rapid, one-off measurements of volume and moisture content for each of 200 undisturbed peds extracted from a field soil, taking measurements as peds slowly dried in the laboratory. The large sample size increased robustness of the shrinkage curve parameter estimates to noise generated by this rapid measurement technique, but a much smaller sample would have resulted in similar parameter estimates. Accepted version

Greenhouse gas (GHG) emissions from crop residue management have been studied extensively, yet the effects of harvesting more than one crop residue in a rotation have not been reported. Here, we measured the short-term changes in methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions in response to residue removal from continuous corn (Zea mays L.) (CC) and corn–wheat (Triticum aestivum L.)–soybean (Glycine max L. Merr.) (CWS) rotations in the Mid-Atlantic USA. A first experiment retained five corn stover rates (0, 3.33, 6.66, 10, and 20 Mg ha−1) in a continuous corn (CC) in Blacksburg, VA, in 2016 and 2017. Two other experiments, initiated during the wheat and corn phases of the CWS rotation in New Kent, VA, utilized a factorial combination of retained corn (0, 3.33, 6.66, and 10.0 Mg ha−1) and wheat residue (0, 1, 2, and 3 Mg ha−1). Soybean residue was not varied. Different crop retention rates did not affect CO2 fluxes in any of the field studies. In Blacksburg, retaining 5 Mg ha−1 stover or more increased CH4 and N2O emissions by ~25%. Maximum CH4 and N2O fluxes (4.16 and 5.94 mg m−2 day−1) occurred with 200% (20 Mg ha−1) retention. Two cycles of stover management in Blacksburg, and one cycle of corn or wheat residue management in New Kent did not affect GHG fluxes. This study is the first to investigate the effects of crop residue on GHG emissions in a multi-crop system in humid temperate zones. Longer-term studies are warranted to understand crop residue management effects on GHG emissions in these systems. Published version

Conservation management practices - including agroforestry, cover cropping, no-till, reduced tillage, and residue return - have been applied for decades to control surface runoff and soil erosion, yet results have not been integrated and evaluated across cropping systems. In this study we collected data comparing agricultural production with and without conservation management strategies. We used a bootstrap resampling analysis to explore interactions between practice type, soil texture, surface runoff, and soil erosion. We then used a correlation analysis to relate changes in surface runoff and soil erosion to 13 other soil health and agronomic indicators, including soil organic carbon, soil aggregation, infiltration, porosity, subsurface leaching, and cash crop yield. Across all conservation management practices, surface runoff and erosion had respective mean decreases of 67% and 80% compared with controls. Use of cover cropping provided the largest decreases in erosion and surface runoff, thus emphasizing the importance of maintaining continuous vegetative cover on soils. Coarse- and medium-textured soils had greater decreases in both erosion and runoff than fine-textured soils. Changes in surface runoff and soil erosion under conservation management were highly correlated with soil organic carbon, aggregation, porosity, infiltration, leaching, and yield, showing that conservation practices help drive important interactions between these different facets of soil health. This study offers the first large-scale comparison of how different conservation agriculture practices reduce surface runoff and soil erosion, and at the same time provides new insight into how these interactions influence the improvement or loss of soil health. (C) 2021 International Research and Training Center on Erosion and Sedimentation, China Water and Power Press, and China Institute of Water Resources and Hydropower Research. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. Research, Terrestrial Ecosystem Sciences Program [DE-AC05-76RL01830]; Yangling Vocational & Technical College 2019 Natural Science Research Fund Project [A2019048]; U.S. Department of Agriculture NRCS Conservation Innovation Grant [69-3A75-14-260]; Virginia Agricultural Experiment Station; Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture Published version Research as part of the Terrestrial Ecosystem Sciences Program, under contract DE-AC05-76RL01830. Can Du was supported by the Yangling Vocational & Technical College 2019 Natural Science Research Fund Project, under grant number: A2019048. Ryan Stewart was supported by the U.S. Department of Agriculture NRCS Conservation Innovation Grant (No. 69-3A75-14-260) and the Vir-ginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture.

HighlightsNatural sediments labeled with rare earth elements can effectively be used as tracers for quantifying fine sediment transport and deposition.Two artificial floods in a small stream (100 ha watershed, 1.5 year return flow of 515 L s-1) transported fine sediment 0 m to >850 m at a maximum flow rate of 55 L s-1.Sediment deposition per unit area was greater in the channel than in the near-channel floodplain.Use of two distinct tracers demonstrated resuspension extent during sequential high-flow events.Presence of large wood in the channel was associated with reduced streamflow rate, decreased suspended sediment transport velocity, increased channel sediment deposition, and reduced near-floodplain sediment deposition.Abstract. Effective sediment management requires an understanding of the lag time between best management practice implementation and observable changes in the target water body. To improve our understanding of sediment lag times, we tested a method to label locally sourced sediments with rare earth elements to quantify fine sediment flow-through and storage in fluvial systems. We injected sediments labeled with lanthanum and ytterbium into a small stream during two artificial flood events. During the floods, we collected and quantified suspended sediments and sediment deposition in the stream channel and floodplain at four cross-sections within our study reach. Two down-gradient (90 m and 850 m) time-integrated suspended sediment samplers evaluated total travel distance. Sediment tracer observations of particle transport distances ranged from 0 m to at least 850 m at a maximum flow rate of 55 L s-1 (stream 1.5 year flow was 515 L s-1). Sediment deposition per unit area was greater in the channel than in the floodplain. The majority of sediment tracer mass injected into the stream entered storage within the first 69 m of the reach. Some particles that deposited following the first flood were resuspended and either transported downstream or redeposited within the study reach. Our results support the further use of rare earth elements as sediment tracers to inform water quality and sediment transport models, and to provide estimates of lag times between management actions and downstream improvements. Keywords: Fine sediment, Flood, Fluvial geomorphology, Lag time, Large wood, Rare earth elements, Sediment deposition, Sediment transport, Tracer.

Subsurface injection of liquid manure is a no-till compatible application method that may fundamentally change nutrient cycling dynamics. This study investigated subsurface injection and surface broadcast application methods on soil nitrate-nitrogen (NO3–-N) at 0, 1, 2, 4, 6, 8, 10, 14, 18, and 22 weeks after first-year applications of liquid dairy slurry in 0 to 15 cm and 15 to 30 cm sampling depths. The effect on corn (Zea mays L.) grain yield and quality parameters was considered. Soil health was assessed by proxy on weeks 0, 2, 8, 14, and 22 by two microbial indicators sensitive to change: carbon (C) mineralization and microbial biomass C. Soil NO3–-N and the microbial indicators were also measured at distances from an injected band of manure: In-band, 10 cm, 20 cm, and 36 cm. The injection application resulted in significantly (p 0.05) different between treatments. Carbon mineralization was significantly (p 0.05) different from the no-manure control. Microbial biomass C was significantly (p

Soil organic matter (SOM) retains and attenuates many contaminants; however, its interactions with neonicotinoid insecticides under field conditions remain poorly understood. The goal of this study was to determine if SOM influences the persistence or leaching of two neonicotinoid insecticides: thiamethoxam (TMX) and its transformation-product clothianidin (CLO). Thiamethoxam-coated soybean [Glycine max (L.) Merr.] was planted into a clay soil containing different soil organic carbon (SOC) concentrations. Leachate and soil samples were collected for 10 wk after planting and were analyzed for insecticide concentrations using liquid chromatography–tandem mass spectrometry. Single and multiple linear regressions were performed between SOC, leaching volumes, and measured insecticide concentrations, focusing on rainfall events near the beginning, middle, and end of the study. Correlations were also tested between SOC and cumulative mass of leached insecticides. Neither SOC nor per-event leachate volumes explained variability in TMX leaching or residual CLO concentrations in soils; however, by the conclusion of the study residual thiamethoxam concentrations in soil were negatively correlated with cumulative volume of leached water. Initially, the concentration and total mass of leached CLO were significantly and negatively correlated with SOC content; however, this effect faded with time. Leachate dynamics also affected CLO transport, with positive correlations between leachate volume and CLO concentration during the latter events. This analysis demonstrates that SOM can reduce peak loading of neonicotinoids but may not alter cumulative leaching over the entire growing season. Funding for this work was provided by the USDA National Institute of Food and Agriculture (Grant 2018-67019-27851) and by the Virginia Agricultural Experiment Station and the Hatch Program of the USDA National Institute of Food and Agriculture (1026126). Published version

Sorptivity is a crucial parameter for modeling water infiltration into soils. Many works have related sorptivity to the soil hydraulic functions, i.e., the water retention and unsaturated hydraulic functions. Parlange's (1975) formulation is one of the most used to relate sorptivity to the soil hydraulic functions, allowing the direct computation of sorptivity as a function of the soil hydraulic parameters and initial and final water contents. On this basis, several works investigated the possibility of direct analytical relationships between sorptivity and the hydraulic shape and scale parameters (e.g., Lassabatere et al., 2021). So far, most of the studies have focused on single permeability soils with monomodal water retention and unsaturated hydraulic functions. However, the use of dual- or multi-permeability approaches is increasing in relation to the necessity to account for preferential flows in soils. The approach developed by (Gerke and van Genuchten, 1993) or (Pollacco et al., 2017) are examples of dual-permeability approaches and allow the modeling of preferential flows in soils. In the proposed study, we apply the formulation proposed by Parlange (1975) for the computation of sorptivity for dual-permeability soils, considering the approaches proposed by Gerke and van Genuchten (1993) and Pollacco et al. (2017). Our developments lead to a relation between the bulk sorptivity of the dual permeability soils to those of the matrix and the fast-flow compartments, plus additional terms. We end with the scaling of the proposed relation for investigating the effects of the matrix and fast-flow shape and scale parameters and the volumetric content occupied by the fast-flow compartment.ReferencesGerke, H. H. and van Genuchten, M. T.: A dual-porosity model for simulating the preferential movement of water and solutes in structured porous-media, 29, 305–319, 1993.Lassabatere, L., Peyneau, P.-E., Yilmaz, D., Pollacco, J., Fernández-Gálvez, J., Latorre, B., Moret-Fernández, D., Di Prima, S., Rahmati, M., Stewart, R. D., Abou Najm, M., Hammecker, C., and Angulo-Jaramillo, R.: Scaling procedure for straightforward computation of sorptivity, 2021, 1–33, https://doi.org/10.5194/hess-2021-150, 2021.Parlange, J.-Y.: On Solving the Flow Equation in Unsaturated Soils by Optimization: Horizontal Infiltration, 39, 415–418, 1975.Pollacco, J. A. P., Webb, T., McNeill, S., Hu, W., Carrick, S., Hewitt, A., and Lilburne, L.: Saturated hydraulic conductivity model computed from bimodal water retention curves for a range of New Zealand soils, 21, 2725–2737, https://doi.org/10.5194/hess-21-2725-2017, 2017.

Water-repellent soils usually experience water flow impedance during the early stage of a wetting process followed by progressive increase of infiltration rate. Current infiltration models are not formulated to describe this peculiar process. Similarly, simplified methods of soil hydraulic characterization (e.g., BEST) are not equipped to handle water-repellent soils. Here, we present an adaptation of the BEST method, named BEST-WR, for the hydraulic characterization of soils at any stage of water-repellency. We modified the Haverkamp explicit transient infiltration model, included in BEST for modeling infiltration data, by embedding a scaling factor describing the rate of attenuation of infiltration rate due to water repellency. The new model was validated using analytically generated data, involving soils with different texture and a dataset that included data from 60 single-ring infiltration tests. The scaling factor was used as a new index to assess soil water repellency in a Mediterranean wooded grassland, where the scattered evergreen oak trees induced more noticeable water repellency under the canopies as compared to the open spaces. The new index produced results in line with those obtained using the water drop penetration time test, which is one of the most widely test applied for quantifying soil water repellency persistence. Finally, we used BEST-WR to determine the hydraulic characteristic curves under both hydrophilic and hydrophobic conditions.

Peatland functions (e.g., carbon sequestration and flora diversity) are largely driven by soil moisture dynamics and thus dependent on interactions between hydrologic regimes and organic soil properties. Understanding these interactions is particularly important in drained peatlands, where drier conditions may alter soil properties with feedbacks to soil water retention and associated ecosystem functions. In this work, we focused on the Great Dismal Swamp (GDS) in Virginia, USA, a historically drained, temperate peatland with ongoing hydrologic restoration efforts. Two distinct soil layers varying in thickness exist at GDS: an upper layer with subangular blocky structure thought to be a result of past drainage, and a sapric lower layer with a massive structure more representative of an undisturbed state. To understand the occurrence and consequences of these distinct layers, we used continuous water table data and analysed soil physical and hydraulic properties to characterize soil profiles at 16 locations. We found significant differences between layer properties, where upper layers had lower fibre and organic matter contents and higher bulk densities. Further, moisture release curves demonstrated lower water retention in upper layers compared with lower layers and key differences in pore structure, with upper layers having higher macroporosity. Upper layers varied in thickness across sampling locations (similar to 0.30 to 1.0 m) with a transition to lower soil layers typically occurring at depths below contemporary water level observations, suggesting that the upper layer may be a result of historical drainage and deeper water table conditions. Yet, upper layers with more frequent saturation exhibited higher water retention and lower macroporosity compared with drier upper layers, thus indicating potential recovery following re-wetting efforts. These findings highlight how past drainage influences soil properties and water retention, with important implications for current management objectives at GDS and other drained peatland systems. U.S. Fish and Wildlife ServiceUS Fish & Wildlife Service Published version This work was funded by the U.S. Fish and Wildlife Service. Special thanks to Brooke Bass, Gavin Washburn, Karen Balentine, and Daniel Franz for their data collection support and to David Mitchem and Brandon Lester for their laboratory assistance.

Liquid manures are typically applied via surface broadcasting; however, subsurface injection is an alternative characterized by greater nutrient retention and a spatially distinct application pattern, altering management strategies and nutrient cycling dynamics. Thus, a field study was conducted from spring of 2016 through fall of 2018 on seven sites to assess pre-sidedress nitrate test (PSNT) methodology, seasonal soil nitrate nitrogen (NO3−-N) trends, corn (Zea mays L.) silage and grain yield, estimated milk production via MILK 2006, and biological soil health among surface broadcast and subsurface injection applications of dairy slurry. A weighted sampling method had a coefficient of variation of 37%, ~8% higher relative to random (28%) and equispaced (30%) sampling methods. Soil NO3−-N was greater in 7 out of 25 measurements under subsurface injection and 30% higher under injection on average during the corn PSNT. There were no significant differences in crop yield or milk production between surface and injected slurry applications, but means were always higher for injection. Biological soil health tests were highly variable, and analyzing carbon mineralization (C-min) took considerably more time than other tests. There were no significant differences in C-min between manure application methods; although, mineralization values increased with soil organic matter. Estimated microbial biomass was on average 46% lower under subsurface injection relative to surface broadcast in 2017, but results were inconsistent in 2016 and 2018. Overall, the biological indicators of soil health were not productive in showing differences between application methods. Nevertheless, it is apparent that injection can decrease chemical sidedress N applications, and either the standard method of PSNT soil sampling or an equispaced method can be used in injected fields.

Land application of manure, while beneficial to soil health and plant growth, can lead to an overabundance of nutrients and introduction of emerging contaminants into agricultural fields. Compared with surface application of manure, subsurface injection has been shown to reduce nutrients and antibiotics in surface runoff. However, less is known about the influence of subsurface injection on the transport and persistence of antibiotic-resistant microorganisms. We simulated rainfall to field plots at two sites (one in Virginia and one in Pennsylvania) 1 or 7 d after liquid dairy manure surface and subsurface application (56 Mg ha–1) and monitored the abundance of culturable antibiotic-resistant fecal coliform bacteria (ARFCB) in surface runoff and soils for 45 d. We performed these tests at both sites in spring 2018 and repeated the test at the Virginia site in fall 2019. Manure subsurface injection, compared with surface application, resulted in less ARFCB in surface runoff, and this reduction was greater at Day 1 after application compared with Day 7. The reductions of ARFCB in surface runoff because of manure subsurface injection were 2.5–593 times at the Virginia site in spring 2018 and fall 2019 and 4–5 times at the Pennsylvania site in spring 2018. The ARFCB were only detectable in the 0-to-5-cm soil depth within 14 d of manure surface application but remained detectable in the injection slits of manure subsurface-injected plots even at Day 45. This study demonstrated that subsurface injection can significantly reduce surface runoff of ARFCB from manure-applied fields. National Institute of Food and Agriculture,Grant/Award Number: 2017-67019-26401; USDA REISS, Grant/Award Number:PEN04574/1004448 Published version

Made available in DSpace on 2022-04-28T19:44:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Consiglio Nazionale delle Ricerche European Regional Development Fund Università degli Studi di Sassari Agence Nationale de la Recherche Ministero dell’Istruzione, dell’Università e della Ricerca Understanding linkages between heterogeneous soil structures and non-uniform flow is fundamental for interpreting infiltration processes and improving hydrological simulations. Here, we utilized ground-penetrating radar (GPR) as a non-invasive technique to investigate those linkages and to complement current traditional methods that are labor-intensive, invasive, and non-repeatable. We combined time-lapse GPR surveys with different types of infiltration experiments to create three-dimensional (3D) diagrams of the wetting dynamics. We carried out the GPR surveys and validated them with in situ observations, independent measurements and field excavations at two experimental sites. Those sites were selected to represent different mechanisms that generate non-uniform flow: (1) preferential water infiltration initiated by tree trunk and root systems; and (2) lateral subsurface flow due to soil layering. Results revealed links between different types of soil heterogeneity and non-uniform flow. The first experimental site provided evidence of root-induced preferential flow paths along coarse roots, emphasizing the important role of coarse roots in facilitating preferential water movement through the subsurface. The second experimental site showed that water infiltrated through the restrictive layer mainly following the plant root system. The presented approach offers a non-invasive, repeatable and accurate way to detect non-uniform flow. Department of Agricultural Sciences University of Sassari, Viale Italia, 39A Desertification Research Center University of Sassari, Viale Italia, 39 Univ Lyon Université Claude Bernard Lyon 1 CNRS ENTPE UMR5023 LEHNA Department of Architecture Design and Urban Planning University of Sassari, Via Piandanna, 4 School of Agriculture São Paulo State University (UNESP) Fazenda Experimental Lageado School of Plant and Environmental Sciences Virginia Polytechnic Institute and State University Department of Land Air and Water Resources University of California Department of Chemistry and Pharmacy University of Sassari, Via Piandanna 4 Research Group in Forest Science and Technology (Re-ForeST) Universitat Politècnica de València, Camí de Vera Institute of Sciences and Technologies for Sustainable Energy and Mobility (STEMS) National Research Council of Italy, Strada delle Cacce, 73 School of Agriculture São Paulo State University (UNESP) Fazenda Experimental Lageado Agence Nationale de la Recherche: ANR-17-CE04-0010 Ministero dell’Istruzione, dell’Università e della Ricerca: J54I18000120001

Many ecosystems are being severely degraded, leading the United Nations to deem 2021-2030 as the Decade on Ecosystem Restoration. To be successful, this effort requires robust monitoring tools to assess land reclamation practices. Our study aimed to evaluate the quality of recovery efforts in mined areas by developing a Recovery Quality Index (RQI) based on soil and vegetation indicators. Using the heavily mined Iron Quadrangle region of Brazil as an example, we selected four local, undisturbed reference areas as restoration goals: Atlantic Forest (AF); ferruginous rupestrian grassland with dense vegetation (FRGD); ferruginous rupestrian grassland with sparse vegetation (FRGS); and quartzite rupestrian grassland (QRG). We also selected four areas that were directly or indirectly affected by mining, including an environmental compensation area set aside 5 years prior to the study (COMP-5), two sterile piles that had undergone recovery for 15 and 20 years (SP-20 and SP-15), and a cave area with 15 years of recovery (CAVE-15). The four recovery areas were grouped together with each individual reference area (making four combinations of sites), and measurements of 2 vegetation parameters and 34 soil attributes were used in a Principal Component Analysis (PCA) for each grouping. We determined the RQI for each group by summing weighted PCA scores for responsive indicators. Vegetative parameters had the lowest RQI weights in all four groups. Soil physical indicators tended to be the most important, except in AF, where chemical indicators were most relevant. RQI values were also lowest when AF was used as the reference, showing that the forest was a unique ecosystem, and the CAVE-15 site had lower RQI scores than the other restored sites, indicating the high degree of disturbance that occurred in that low-lying area. The SP-20 site tended to have higher RQI values than the SP-15, and similar values to the less disturbed COMP-5 areas, potentially indicating greater recovery of native soil properties during the longer recovery period. This RQI-based approach has excellent potential for robust assessment of the recovery of areas degraded by mining and can support decision-making during monitoring.

Preferential flow reduces water residence times and allows rapid transport of pollutants such as organic contaminants. Conventional understanding of solute transport implies that preferential flow reduces the influence of soil matrix-solute interactions; however, this assumption lacks robust validation in the field. To better understand how physicochemical properties affect solute transport across a range of preferential flow conditions, we applied deuterium-labeled rainfall to field plots containing manure spiked with eight common antibiotics with a range of affinity for the soil. We then quantified preferential flow and solute transport using 48 soil pore water samplers spread along a hillslope. Based on >700 measurements, our data showed that solute transport to lysimeters was similar – regardless of antibiotic affinity for soil – when preferential flow represented less than 15% of the total water flow. When preferential flow exceeded 15%, however, concentrations were higher for compounds with relatively low affinity for soil. These results suggest that bypassing water flow can select for compounds that are more easily released from the soil matrix, thus providing fundamental insight into how flow heterogeneity affects pollutant mobility in soils. Moreover, because these data do not fully align with existing solute transport theory, they may be useful for building improved process-based transport models.

Preferential flow reduces water residence times and allows rapid transport of pollutants such as organic contaminants. Thus, preferential flow is considered to reduce the influence of soil matrix-solute interactions during solute transport. While this claim may be true when rainfall directly follows solute application, forcing rapid chemical and physical disequilibrium, it has been perpetuated as a general feature of solute transport-regardless of the magnitude preferential flow. A small number of studies have alternatively shown that preferential transport of strongly sorbing solutes is reduced when solutes have time to diffuse and equilibrate within the soil matrix. Here we expand this inference by allowing solute sorption equilibrium to occur and exploring how physiochemical properties affect solute transport across a vast range of preferential flow. We applied deuterium-labeled rainfall to field plots containing manure spiked with eight common antibiotics with a range of affinity for the soil after 7 days of equilibration with the soil matrix and quantified preferential flow and solute transport using 48 soil pore water samplers spread along a hillslope. Based on > 700 measurements, our data showed that solute transport to lysimeters was similar-regardless of antibiotic affinity for soil-when preferential flow represented less than 15% of the total water flow. When preferential flow exceeded 15%, however, concentrations were higher for compounds with relatively low affinity for soil. We provide evidence that (1) bypassing water flow can select for compounds that are more easily released from the soil matrix, and (2) this phenomenon becomes more evident as the magnitude of preferential flow increases. We argue that considering the natural spectrum preferential flow as an explanatory variable to gauge the influence of soil matrix-solute interactions may improve parsimonious transport models. National Institute of Food and Agriculture, U.S. Department of Agriculture [2017-67019-26401, 2018-67019-27851]; Virginia Agricultural Experiment Station; Hatch program of the National Institute of Food and Agriculture, U.S. Department of Agriculture [1026126] Published version This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Grants 2017-67019-26401 and 2018-67019-27851. Funding was also provided in part by the Virginia Agricultural Experiment Station and the Hatch program of the National Institute of Food and Agriculture, U.S. Department of Agriculture (1026126).

Hydraulic conductivity (K) is a key hydrologic parameter widely recognized to be difficult to estimate and constrain, with little consistent assessment in disturbed, urbanized soils. To estimate K, it is either measured, or simulated by pedotransfer functions, which relate K to easily measured soil properties. We measured K in urbanized soils by double-ring infiltrometer (K(dring)), near-saturated tension infiltrometry (K(minidisk)), and constant head borehole permeametry (K(borehole)), along with other soil properties across the major soil orders in 12 United States cities. We compared measured K with that predicted from the pedotransfer function, ROSETTA. We found that regardless of soil texture, K(dring) was consistently larger than K(minidisk); with the latter having slightly less sample variance. K(borehole) was dependent upon specific subsurface conditions, and contrary to common expectations, did not always decrease with depth. Based on either soil textural class, or percent textural separates (sand, silt clay), ROSETTA did not accurately predict measured K for surface nor subsurface soils. We go on to discuss how K varies in urban landscapes, the role of measurement methods and artifacts in the perception of this metric, and implications for hydrologic modeling. Overall, we aim to inspire consistency and coherence when addressing K-related challenges in sustainable urban water management.

Soil water repellency induced by wildfires can alter hydraulic properties and hydrologic processes; however, the persistence and vertical position (i.e., depth) of water‐repellent layers can vary between systems and fires, with limited understanding of how those variations affect infiltration processes. This study occurred in two forested locations in the south‐central Appalachian Mountains that experienced wildfires in late 2016: Mount Pleasant Wildfire Refuge, Virginia, and Chimney Rock State Park, North Carolina. In each location, sites were selected to represent unburned conditions and low to moderate burn intensities. At each site, we measured the soil water repellency at the surface (ash layer or O horizon) and ~2 cm below the surface (A horizon) using the water drop penetration time method (n = 10–14). Soil water content was also measured over the upper 10 cm of the soil (n = 10), and infiltration tests were conducted using a tension infiltrometer (n = 6–8). The results showed that soil repellency was highest in the surface layer at the Mount Pleasant location and was highest in the subsurface layer at the Chimney Rock location. Soil water content was lower in unburned soil than in burned soil, especially for measurements taken immediately postfire, with soil water content negatively correlated with water repellency. Water repellency in the surface layer significantly reduced relative infiltration rates (estimated as differences between initial and steady‐state rates), whereas subsurface water repellency did not affect relative infiltration. As a result, water repellency persisted longer in sites with surface as opposed to subsurface water repellency. Finally, differences between burned and unburned sites showed that although the wildfires increased the occurrence of water repellency, they did not alter the underlying relationship between relative infiltration and water repellency of the surface soil.

Neonicotinoid insecticides provide crop protection via water solubility and systemicity, yet these chemical characteristics, combined with high toxicity to non-target invertebrates (e.g., honeybees), elicit concern of environmental transport. Neonicotinoids have been detected in soil and surface water throughout North America; however, no investigation has defined a direct connection to planted seed dressings. We quantified the physical transport of thiamethoxam (TMX), a neonicotinoid, under field conditions. We planted TMX-coated corn seeds and maintained plots with and without viable crops (n = 3 plots per treatment) to determine plant influence on pesticide transport. TMX concentrations were measured in soil and drainage throughout the growing season. Storm-generated runoff was the dominant transport mechanism (maximum TMX concentration 1.72 ± 0.605 μg L−1; no viable plants), followed by shallow (

Drainage is a globally common disturbance in forested peatlands that impacts peat soils, forest communities, and associated ecosystem functions, calling for informed hydrologic restoration strategies. The Great Dismal Swamp (GDS), located in Virginia and North Carolina, U.S.A., has been altered since colonial times, particularly by extensive ditch networks installed to lower water levels and facilitate timber harvests. Consequently, peat decomposition rates have accelerated, and red maple has become the dominant tree species, reducing the historical mosaic of bald cypress, Atlantic white-cedar, and pocosin stands. Recent repair and installation of water control structures aim to control drainage and, in doing so, enhance forest community composition and preserve peat depths. To help inform these actions, we established five transects of 15 plots each (75 plots total) along a hydrologic gradient where we measured continuous water levels and ecosystem attributes, including peat depths, microtopography, and forest composition and structure. We found significant differences among transects, with wetter sites having thicker peat, lower red maple importance, greater tree density, and higher overall stand richness. Plot-level analyses comported with these trends, clearly grouping plots by transects (via nonmetric multidimensional scaling) and resulting in significant correlations between specific hydrologic metrics and ecosystem attributes. Our findings highlight hydrologic controls on soil carbon storage, forest structure, and maple dominance, with implications for large-scale hydrologic restoration at GDS and in other degraded forested peatlands more broadly. Virginia Tech Department of Forest Resources and Environmental Conservation; U.S. Fish and Wildlife Service Great Dismal Swamp National Wildlife Refuge; U.S. Geological SurveyUnited States Geological Survey This work was funded by the Virginia Tech Department of Forest Resources and Environmental Conservation, U.S. Fish and Wildlife Service Great Dismal Swamp National Wildlife Refuge, and U.S. Geological Survey. ("Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government") Special thanks to Ray Ludwig and Will Doran for data collection assistance and Tal Roberts for technical support. Public domain – authored by a U.S. government employee

Soil aggregate stability influences many biophysical and agronomic processes while acting as a key soil health indicator, yet current quantification methods suffer shortcomings including lack of repeatability, inadequate control over input energy, and inaccuracies in coarse-textured soils or those with multi-modal size distributions. In response, we propose a new method deemed integrated aggregate stability (IAS) to interpret aggregate stability using a laser diffraction (LD) machine. This method corrects for underlying particle-size distributions and provides a comprehensive metric of aggregate stability. As verification, we presented repeatability tests that demonstrate the precision of the IAS method, and then compared IAS measurements to wet sieving results for three different soils. Overall, IAS showed higher correlation with the wet sieving method (R² = 0.49 to 0.59) than the median aggregate size (d50), which represents the most common current method for quantifying aggregate stability (R² = 0.09 to 0.27). Further, IAS can estimate the proportions of macro (>0.25 mm) and micro (

Vertisols shrink and swell with changes in soil moisture, influencing hydraulic properties. Vertisols are often in floodplains, yet the importance of flooding as a source of soil moisture remains poorly understood. We used blue dye and deuterated water as tracers to determine the role of the macropore network in matrix recharge under artificial flood durations of 3 and 31 days in large soil monoliths extracted from a forested soil. Gravimetric soil moisture content increased by 47% in the first three days, then increased only 3.5% from day 3-31. Post-flood moisture content was greatest in the organic-rich, top 10 cm and was lower at 10-75 cm where organic matter was less. Deuterium concentration revealed that soil moisture in the top 10 cm was quickly dominated by artificial flood water, but at depth remained

Sorptivity is a parameter of primary importance in the study of unsaturated flow in soils. This integral parameter is often considered for modeling the computation of water infiltration into vertical soil profiles (1D or 3D axisymmetric geometry). Sorptivity can be directly estimated from the knowledge of the soil hydraulic functions (water retention of hydraulic conductivity), using the integral formulation of Parlange (Parlange, 1975). However, it requires the prior determination of the soil hydraulic diffusivity and its numerical integration between the initial and the final saturation degrees, which may be tricky for some instances (e.g., coarse soil with diffusivity functions quasi-infinite close to saturation). In this paper, we present a specific scaling procedure for the computation of sorptivity considering slightly positive water pressure heads at the soil surface and initial dry conditions (corresponding to most water infiltration on the field). The square sorptivity is related to the square dimensionless sorptivity (referred to as cp parameter) corresponding to a unit soil (i.e., unit values of all the scaled parameters and zero residual water content) utterly dry at the initial state and saturated at the final state. The cp parameter was computed numerically and analytically for five current models: delta functions (Green and Ampt model), Brooks and Corey, van Genuchten-Mualem, van Genuchten-Burdine, and Kosugi models as a function of the shape parameters. The values are tabulated and can be easily used to determine any dimensional sorptivity value for any case. We propose brand-new analytical expressions for some of the models and validate previous formulations for the other models. Our numerical results also showed that the relation between the cp parameters and shape parameters strongly depends on the chosen model, with either increasing or decreasing trends when moving from coarse to fine soils. These results highlight the need for carefully selecting the proper model for the description of the water retention and hydraulic conductivity functions for the rigorous estimation of sorptivity. Present results show the need to understand better the hydraulic model's mathematical properties, including the links between their parameters, and, secondly, to better relate these properties to the physical processes of water infiltration into soils.

Gas diffusion is a primary driver of carbon dioxide (CO2) movement through unsaturated soils. In typical soils, high soil concentrations of CO2 caused by autotrophic and heterotrophic respiration cause the gas to primarily diffuse upward. However, karst landscapes can have subsurface CO2 sinks, both due to CaCO3 weathering and losses via underlying caves and fracture networks. In this study our objective was to quantify the magnitude and direction of CO2 fluxes in a pastured karst system located in Southwest Virginia (James Cave). Our hypotheses were: 1) the zero-flux plane, or location of maximum CO2 concentration within the soil profile, is located at deeper depths, ≥60 cm depth during warmer months of the year and located at shallower depths, ≤60 cm, during the colder months of the year, 2) the zero-flux plane will exist ˂60 cm depth at the sinkhole location more often than at the upslope locations, and 3) CO2 fluxes will be primarily upward during the growing season and primarily downward during the colder months of the year. We installed paired CO2 and soil moisture sensors at 20 cm, 40 cm, and 60 cm depths, with profiles installed in the shoulder, midslope, and bottom (i.e., sinkhole) of a hillslope adjacent to the cave entrance. The sensors recorded hourly data between 7 February 2017 and 13 September 2019. The depth of the zero-flux plane was identified by the depth of maximum CO2 concentration for each profile, while the measured concentration gradient from 20 to 60 cm was used to estimate CO2 flux with Fick’s Law. Our findings support our hypotheses that the relative location of the zero-flux plane was located more often at deeper depths during warmer months of the year and located at shallower depths, i.e. ˂60 cm, during colder months of the year. The zero-flux plane was more frequently shallow (i.e., ˂60 cm) at the sinkhole location compared to the upslope profiles. The CO2 fluxes reflected upward movement during the growing season and downward movement during the colder months of the year. We speculate that these processes reflect the influence of the underlying cave system, which may serve as a CO2 sink during colder months, when the cave becomes vented via natural convection. Altogether, these findings suggest that downward diffusion may be an important yet oft-overlooked component of carbon fluxes in karst landscapes.

Preferential flow is more the rule than the exception. Water infiltration is often led by preferential flow due to macropores, specific soil structures (e.g., aggregates, macropore networks), or lithological heterogeneity (occurrence of materials with contrasting hydraulic properties). Water infiltration in soils prone to preferential flow strongly depends on soil features below the soil surface, but also the initiation of water infiltration at the surface. When the macropore networks are not dense, with only a few macropores intercepting the soil surface, water infiltration experiments with ring size in the order of 10-15 cm diameter may overlook sampling macropore networks during some infiltration runs, minimizing the effect of macropore flow on the bulk water infiltration at the plot scale.In this study, we investigated the effect of ring size on water infiltration into soils prone to preferential flow. We used two ring sizes: small (15 cm in diameter) and large (50 cm in diameter). By doing so, we hypothesized that the large rings, sampling a more representative soil volume, will maximize the probability to intercept and activate a macropore network. In contrast, the small rings may activate the macropore network only occasionally, with other infiltration runs mainly sampling the soil matrix. Thus, the small rings are expected to provide more variable results. On the other hand, the large rings are expected to provide more homogeneous results in line with the soil's bulk infiltration capability, including all pore networks at the plot scale.Three different sites were sampled with varying types of preferential flow (macropore-induced versus lithological heterogeneity induced). The experimental plan included inserting large rings at several places in the experimental sites with a dozen small rings nearby to sample the same soil. All the rings were submitted to a similar positive constant water pressure head at the soil surface. The cumulative infiltrations were then monitored and treated with BEST algorithms to get the efficient hydraulic parameters. Note that the cumulative infiltration could not be compared directly since lateral water fluxes varied in extent and geometry between the different ring sizes. The impacts of the ring size on the magnitude of cumulative infiltration and related estimated hydraulic parameters were discussed. Our results demonstrated the impact of ring size but also the dependency of such effect on the site and the type of flow.Our results contribute to understanding preferential flow in heterogeneous soils and the complexity of its measure using regular water infiltration devices and protocols.

Time-lapse ground penetrating radar (GPR) surveys in conjunction with automated single-ring infiltration experiments can be used for non-invasive monitoring of the spatial distribution of infiltrated water and for generating 3D representations of the wetted zone. In this study we developed and tested a protocol to quantify and visualize water distribution fluxes under unsaturated and saturated conditions into layered soils. We carried out a gridded GPR survey on a 0.3-m thick sandy clay loam layer underlain by a restrictive limestone layer at the Ottava experimental station of the University of Sassari (Sardinia, IT). We firstly established a survey grid (1 m × 1 m), consisting of six horizontal and six vertical parallel survey lines with 0.2 m intervals between them. The field survey then consisted of six steps, including i) a first GPR survey, ii) a tension infiltration experiment conducted within the grid and aimed at activating only the soil matrix, iii) a second GPR survey aimed at highlighting the amplitude fluctuations between repeated GPR radargrams of the first and second surveys, due to the infiltrated water moving within the matrix flow region, iv) a single-ring infiltration experiment of the Beerkan type carried out within the grid on the same infiltration surface using a solution of brilliant blue dye (E133) and aimed to activate the whole pore network, v) a third GPR survey aimed to highlight the amplitude fluctuations between repeated GPR radargrams of the first and third surveys, due to the infiltrated water moving within the whole pore network (both matrix and fast-flow regions), and vi) the excavation of the soil to expose the wetted region. The shapes of the 3D diagrams of the wetted zones facilitated the interpretation of the infiltrometer data, allowing us to resolve water infiltration into the layered system. Finally, we used the infiltrometer data in conjunction with the Beerkan estimation of soil transfer parameter (BEST) method to determine the following capacitive indicators of soil physical quality of the upper soil layer: air capacity AC (m3 m–3), plant-available water capacity PAWC (m3 m–3), relative field capacity RFC (–), and soil macroporosity pMAC (m3 m–3). Results showed that the investigated soil was characterized by high soil aeration and macroporosity (i.e., AC and pMAC) along with low values for indicators associated with microporosity (i.e., PAWC and RFC). These findings suggest that the upper soil layer facilitates root proliferation and quickly drains excess water towards the underlying limestone layer, and, on the contrary, has limited ability to store and provide water to plant roots. In addition, the 3D diagram allowed the detection of non-uniform downward water movement through the restrictive limestone layer. The detected difference between the two layers in terms of hydraulic conductivity suggests that surface ponding and overland flow generation occurs via a saturation-excess mechanism. Indeed, percolating water may accumulate above the restrictive limestone layer and form a shallow perched water table that, in case of extreme rainfall events, could rise causing the complete saturation of the soil profile.

Increasing frequency of wildfire in humid hardwood forests make it necessary to understand the occurrence and origin of soil water repellency in these systems, as wildfire-induced soil water repellency has been observed to severely impact many biophysical processes in other forest types. In this project, we studied two sites in the Appalachian Mountains, United States, (at Mount Pleasant Wildlife Refuge, Virginia, and Chimney Rock State Park, North Carolina) where wildfires occurred in late 2016. In each site, burned and unburned soils were evaluated for actual (in the field) and potential (in the laboratory) water repellency using the water drop penetration time method. In addition, samples were analyzed for organic carbon content (measured using C/N analyzer), hydrophobic functional groups (using Fourier transform infrared, FTIR), and their rank correlations (rs) based on multiple samples collected one year after the fires. We found that soil water repellency was substantial greater in burned soils in the first months after the fire, and persisted for the entire year in the more severely burned soils. We also determined that potential water repellency was much greater than actual water repellency, and that organic carbon content and hydrophobic functional groups were significantly correlated to potential water repellency (p < 0.0001). Correlations were stronger at Mount Pleasant (0.77 < rs s < 0.70). For actual water repellency only had significant correlations with soil organic content at Mount Pleasant (p < 0.0001), and with hydrophobic functional groups (p < 0.0001) at both sites except the unburned soils at Chimney Rock. However, these correlations were weaker than with potential water repellency, likely due to the influence of soil water content. Altogether, this study provides new insight into the influence of soil organic matter and its composition on post-wildfire soil water repellency.

Stewart and Abou Najm (2018) developed a comprehensive model (SA model) for single ring infiltration that consists of a couple of two-terms explicit infiltration equations similar, in form, to the approximate expansions proposed by Haverkamp et al. (1994) (HV model). Application of SA model requires the transition time, τcrit, from transient to steady state to be known a-priori or establishing a constraint among the four constants that figure in the infiltration equations. Estimation of soil saturated hydraulic conductivity, Ks, and capillary length, λ, from single ring infiltration measurements also needs a scaling parameter referred to “a” to be known. SA model assumes this scaling parameter as a constant and fixes its value at a = 0.45. However, there is evidence that a cannot be considered a constant independent of soil type and initial water content.This study investigates some open issues related to the use of the SA model for single ring infiltration: 1) how comparable is τcrit with the maximum time, tmax, that separates transient from steady state condition in HV model; 2) how the scaling parameter a depends on different experimental conditions and how it can be related to HV parameters.Preliminary theoretical considerations showed that the two characteristic times (τcrit and tmax) are related and, for relatively dry initial conditions, parameter a depends only on the soil type and ring radius being maximum for small ring radii or soils with high capillarity (a = 1) and minimum for large rings or coarse soils (a = 0.467).An optimization procedure, with a constraint among the four infiltration constants, was applied to fit the SA model to both analytical and experimental infiltration data to derive τcrit and the associated value of a.The analytical data confirmed that the ratio τcrit/tmax was constant and equal to 1.495, regardless the combination of soil, ring diameter and initial water saturation. The calculated a values varied between 0.706 and 0.904, with a mean equal to a = 0.807, and were independent of the initial water content for saturation degrees up to approximately 0.50.Application of the optimization procedure to field data was problematic given it was successful only in 29 out of 70 infiltration tests. Fixing τcrita-priori could be advisable in this case and it was shown that two alternative empirical criteria for selecting τcrit yielded a values differing by a nearly negligible mean factor of 1.10 and significantly correlated to one another (R2 = 0.997).However, a rather high percentage of a values (45.5%) were greater than the theoretical maximum value (a = 1), and therefore were physically implausible. Excluding these values from the analysis, the mean a parameter (a = 0.735) was close to that estimated by the successful applications of the optimization procedure (a = 0.673).Therefore, consistent results were obtained by field and analytical data with a values intermediate between the suggested values in the literature (a = 0.45 and 0.91). These findings can inform parameterization choices for others working with infiltration models, and should reduce uncertainty during interpretation of infiltration measurements.

Research over the past several decades has shown that preferential flow is more the rule than the exception. However, our collective understanding of preferential flow processes has been limited by a lack of suitable methods to detect and visualize the initiation and evolution of non-uniform wetting at high spatial and temporal resolutions, particularly in real-world settings. In this study, we investigate water infiltration initiation by tree trunk and root systems. We carried out time-lapse ground penetrating radar (GPR) surveys in conjunction with a simulated stemflow event to provide evidence of root-induced preferential flow and generate a three-dimensional representation of the wetted zone.We established a survey grid (3.5 m × 5 m, with a local slope of 10.3°), consisting of ten horizontal and thirteen vertical parallel survey lines with 0.5 m intervals between them. The horizontal lines were downslope-oriented. The grid was placed around a Quercus suber L. We collected a total of 46 (2 GPR surveys × 23 survey lines) radargrams using an IDS (Ingegneria Dei Sistemi S.p.A.) Ris Hi Mod v. 1.0 system with a 900-MHz antenna mounted on a GPR cart. Two grid GPR surveys were carried out before and after the artificial stemflow experiment. In the experiment, we applied 100 L of brilliant blue dye (E133) solution on the tree trunk. The stemflow volume of 100 L corresponded to 63.2 mm of incident precipitation, considering a crown projected area of 201 m2 and a 1.3% conversion rate of rainfall to stemflow. Trench profiles were carefully excavated with hand tools to remove soil and detect both root location and size and areas of infiltration and preferential pathways on the soil profile.The majority (84.4%) of artificially applied stemflow infiltrated into the soil, while the remaining 15.6% generated overland flow, which was collected by a small v-shaped plastic channel placed into a groove previously scraped on the downhill side of the tree. The 3D diagram clearly demarcated the dimension and shape of the wetted zone, thus providing evidence of root-induced preferential flow along coarse roots. The wetted zone extended downslope up to a horizontal distance of 3 m from the trunk and down to a depth of approximately 0.7 m. Put all together, this study shows the importance of accounting for plant and trees trunk and root systems when quantifying infiltration.