In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large‐scale infrastructure, in the form of lattice towers, forming ‘arrays’ which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO2 concentrations (e[CO2]) by +150 µmol/mol. In practice, acceptable operational enrichment (ambient [CO2] + e[CO2]) is ±20% of the set point 1‐min average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO2] (April to November 2017), [CO2] measurements in treatment and control arrays show that the target concentration was successfully delivered, that is: +147 ± 21 µmol/mol (mean ± SD) or 98 ± 14% of set point enrichment target. e[CO2] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO2 supply issues (0.6%) or adverse weather conditions (1.1%). CO2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO2 occurred <1% of the time in control arrays. Incidences of cross‐contamination >80 µmol/mol (i.e. >53% of the treatment increment) into control arrays accounted for <0.1% of the enrichment period. The median [CO2] values in reconstructed three‐dimensional [CO2] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next‐generation forest FACE facilities built into tall and complex forest stands.

Time domain reflectometry (TDR) measures the apparent relative dielectric permittivity (ARDP) of a soil and is commonly used to determine the volumetric water content (VWC) of the soil. ARDP is affected by several factors in addition to water content, such as the soil's electrical conductivity, temperature, and density. These relationships vary with soil type and are very soil-dependent, and despite previous research, they are still not fully understood. A multivariate statistical approach (principal component analysis, PCA) is used to describe a range of soils from two separate sites in the UK (clay and silty sandsandy silt). The advantage of a PCA is that it considers several variables at a time, giving an immediate picture of their underlying relationships. It was found that for the studied soils, ARDP was positively correlated with VWC and bulk electrical conductivity, but did not show any dependence on some other geotechnical parameters. TDR has recently been used in geotechnical engineering for measuring the gravimetric water content (GWC) and dry density. However, the current approaches require a custom-made TDR probe and an extensive site specific empirical laboratory calibration. To extend the potential use of TDR in the geotechnical industry, three relatively simple methods are proposed to estimate the GWC from VWC (derived from the measured ARDP values) and dry density depending on the amount of information known about the soil. Examples of possible applications of these methods include continuous monitoring of consolidation adjacent to a structure, the effect of seasonal weather and climate change on ageing earthwork assets, and the shrink-swell potential adjacent to trees. All three methods performed well, with between 83% and 98% of the data lying within a ±5% GWC envelope, with the data for clay soils performing better than those for silty sands -sandy silts. This is partly due to the fact that the applied relationship converting ARDP to VWC performs better for clays than silty sands -sandy silts, as well as less variation of the estimated bulk density that is needed to derive the dry density.Key words: time domain reflectometry, volumetric water content, gravimetric water content, apparent relative dielectric permittivity, principal component analysis, estimation of dry density.Résumé : La réflectométrie dans le domaine temps (RDT) mesure la permittivité diélectrique apparente relative (PDAR) d'un sol, et est communément utilisée pour déterminer la teneur en eau volumique (TEV) de ce sol. La PDAR est affectée par plusieurs facteurs en plus de la teneur en eau, comme la conductivité électrique du sol, la température et la densité. Ces relations varient selon le type de sol, et malgré les recherches antérieures, elles ne sont pas encore bien comprises puisqu'elles dépendent beaucoup du sol. Une approche statistique multivariée (analyse en composantes principales, ACP) est utilisée pour décrire une variété de sols provenant de deux sites différents au Royaume-Uni (argile et sable silteux -...

We address the problem of accurately locating buried utility segments by fusing data from multiple sensors using a novel Marching-Cross-Section (MCS) algorithm. Five types of sensors are used in this work: Ground Penetrating Radar (GPR), Passive Magnetic Fields (PMF), Magnetic Gradiometer (MG), Low Frequency Electromagnetic Fields (LFEM) and Vibro-Acoustics (VA). As part of the MCS algorithm, a novel formulation of the extended Kalman Filter (EKF) is proposed for marching existing utility tracks from a scan cross-section (scs) to the next one; novel rules for initializing utilities based on hypothesized detections on the first scs and for associating predicted utility tracks with hypothesized detections in the following scss are introduced. Algorithms are proposed for generating virtual scan lines based on given hypothesized detections when different sensors do not share common scan lines, or when only the coordinates of the hypothesized detections are provided without any information of the actual survey scan lines. The performance of the proposed system is evaluated with both synthetic data and real data. The experimental results in this work demonstrate that the proposed MCS algorithm can locate multiple buried utility segments simultaneously, including both straight and curved utilities, and can separate intersecting segments. By using the probabilities of a hypothesized detection being a pipe or a cable together with its 3D coordinates, the MCS algorithm is able to discriminate a pipe and a cable close to each other. The MCS algorithm can be used for both post- and on-site processing. When it is used on site, the detected tracks on the current scs can help to determine the location and direction of the next scan line. The proposed “multi-utility multi-sensor” system has no limit to the number of buried utilities or the number of sensors, and the more sensor data used, the more buried utility segments can be detected with more accurate location and orientation.

Time‐Domain Reflectometry (TDR) has been used extensively in the past thirty years in order to measure soil water content and bulk electrical conductivity (ECb), both in the laboratory and in the field. TDR can be effectively used in combination with geophysical techniques such as Ground Penetrating Radar (GPR) in order to provide information on relative dielectric permittivity and ECb. As part of the Mapping the Underworld project, a TDR monitoring station was constructed with the aim of monitoring the geophysical parameters of the soil in a field case study. A rigorous methodology, utilizing the latest knowledge for calibration and analysis was followed and is thoroughly elucidated in this paper. The reasons behind the choice of the equipment setup are described, with the intention of providing a reference for similar TDR field installations. The precision and accuracy of TDR and the validation of the calibration procedures were assessed with laboratory and field tests. The standard deviation of several TDR measurements in the laboratory was on average smaller than 2% for both apparent permittivity and ECb. The accuracy, expressed as the mean difference to reference values, was on average smaller than 2% and 3% of apparent permittivity and ECb respectively, although higher errors, up to ≈ 5% and ≈ 7.5% respectively, were measured in media with very low apparent permittivity (i.e., air) and at ECb values smaller than 0.0010 S/m. These results demonstrate that with the chosen methodology and setup, TDR can provide reliable data and can be used for long‐term geophysical monitoring. The data provided by TDR monitoring stations could contribute to a data base of geophysical properties for soils. This information may eventually be used to assist the fine tuning of shallow geophysical techniques such as GPR.