scholarly journals Use of cosmic ray neutron sensors for soil moisture monitoring in forests

2015 ◽  
Vol 12 (9) ◽  
pp. 9813-9864 ◽  
Author(s):  
I. Heidbüchel ◽  
A. Güntner ◽  
T. Blume
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Soil Samples ◽  
Calibration Function ◽  
Neutron Sensors ◽  
Hydrogen Mass

Abstract. Cosmic ray neutron sensors (CRS) are a promising technique to measure soil moisture at intermediate scales. To convert neutron counts to average volumetric soil water content a simple calibration function can be used (the N0-calibration of Desilets et al., 2010). This calibration function is based on soil water content derived directly from soil samples taken within the footprint of the sensor. We installed a CRS in a mixed forest in the lowlands of north-eastern Germany and calibrated it 10 times throughout one calendar year. Each calibration with the N0-calibration function resulted in a different CRS soil moisture time series, with deviations of up to 0.12 m3 m-3 for individual values of soil water content. Also, many of the calibration efforts resulted in time series that could not be matched with independent in situ measurements of soil water content. We therefore suggest a new calibration function with a different shape that can vary from one location to another. A two-point calibration proved to be adequate to correctly define the shape of the new calibration function if the calibration points were taken during both dry and wet conditions covering at least 50 % of the total range of soil moisture. The best results were obtained when the soil samples used for calibration were linearly weighted as a function of depth in the soil profile and non-linearly weighted as a function of distance from the CRS, and when the depth-specific amount of soil organic matter and lattice water content was explicitly considered. The annual cycle of tree foliation was found to be a negligible factor for calibration because the variable hydrogen mass in the leaves was small compared to the hydrogen mass changes by soil moisture variations. Finally, we provide a best practice calibration guide for CRS in forested environments.

scholarly journals Use of cosmic-ray neutron sensors for soil moisture monitoring in forests

2016 ◽  
Vol 20 (3) ◽  
pp. 1269-1288 ◽  
Author(s):  
Ingo Heidbüchel ◽  
Andreas Güntner ◽  
Theresa Blume
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Soil Samples ◽  
Calibration Function ◽  
Total Range ◽  
Hydrogen Mass

Abstract. Measuring soil moisture with cosmic-ray neutrons is a promising technique for intermediate spatial scales. To convert neutron counts to average volumetric soil water content a simple calibration function can be used (the N0-calibration of Desilets et al., 2010). The calibration is based on soil water content derived directly from soil samples taken within the footprint of the sensor. We installed a cosmic-ray neutron sensor (CRS) in a mixed forest in the lowlands of north-eastern Germany and calibrated it 10 times throughout one calendar year. Each calibration with the N0-calibration function resulted in a different CRS soil moisture time series, with deviations of up to 0.1 m3 m−3 (24 % of the total range) for individual values of soil water content. Also, many of the calibration efforts resulted in time series that could not be matched with independent in situ measurements of soil water content. We therefore suggest a modified calibration function with a different shape that can vary from one location to another. A two-point calibration was found to effectively define the shape of the modified calibration function if the calibration points were taken during both dry and wet conditions spanning at least half of the total range of soil moisture. The best results were obtained when the soil samples used for calibration were linearly weighted as a function of depth in the soil profile and nonlinearly weighted as a function of distance from the CRS, and when the depth-specific amount of soil organic matter and lattice water content was explicitly considered. The annual cycle of tree foliation was found to be a negligible factor for calibration because the variable hydrogen mass in the leaves was small compared to the hydrogen mass changes by soil moisture variations. As a final point, we provide a calibration guide for a CRS in forested environments.

The sensitivity of CRNS and Sentinel-2 products to detect differences in soil water content along a toposequence with two contrasting parent materials

2021 ◽  
Author(s):  
Leticia Gaspar ◽  
Trenton Franz ◽  
Ivan Lizaga ◽  
Borja Latorre ◽  
Ana Navas
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Parent Material ◽  
Low Permeability ◽  
Parent Materials ◽  
The Us ◽  
Neutron Sensors ◽  
Sentinel 2

<p>Soil moisture controls hydrological processes in natural and agricultural systems. A clear understanding of their temporal dynamics and spatial variability is essential to control soil degradation processes, irrigation management and water use efficiency. In recent years, the measurement of soil water content (SWC) with ground-based neutron sensors and remote sensing products have become promising non-invasive methods for different spatial scales. In this study, we are investigating the sensitivity of using cosmic ray neutron sensor (CRNS) and Sentinel-2 SWC index for quantifying different dynamics of soil moisture along a toposequence with underlying contrasting parent materials. For this study, three sites were selected in the upper section (US) soils on limestones correspond to Muschelkalk facies, and another three in the lower section (LS) siliciclastic materials composed of low-permeability marls and claystone formation with primarily silty clay texture (Keuper facies). During two surveys, which correspond to wet (spring 2018/05/05) and dry conditions (summer 2018/08/05), a set of soil moisture data were obtained by using i) portable CRNS backpack, ii) satellite-based information and iii) HS200 sensor Delta-T Devices. The physical composition of the studied soils reflects the clear difference in parent material, with mean content of soil organic carbon of 6% in US against 1% in LW, while the mean clay content was lower in US (21%) than in LS (26%). The infiltration measurements also show different responses for water infiltration capacity, with a much higher mean value of hydraulic conductivity for the soils in the US (317 mm per day), reflecting the karst features, than in the LS (35 mm per day) corresponding to the siliciclastic materials. Our results show similar trends during the two surveys, obtaining significantly lower soil water content on limestones at the US where infiltration processes prevailed thus facilitating leaching and limiting runoff. In contrast, the higher soil water content was on siliciclastic soils at the LS where the low permeability of soils due to the clayed substrate promoted increased runoff. Focusing on the comparison of soil moisture data obtained during the wet and dry surveys, a soil characteristic dependency is observed, with a more different soil moisture state on siliciclastic soils (LS) between the two surveys than for the soils on limestones. Our preliminary results pinpoint that CRNS, Sentinel-2 index and field data captured soil moisture dynamics along the toposequence and demonstrated the sensitivity of neutron sensors and remote sensing products to investigate the effect of parent material on soil water content at sampling scale.</p>

scholarly journals Carbonyl sulfide (OCS) exchange between soils and the atmosphere affected by soil moisture and compensation points

2018 ◽  
Author(s):  
Rüdiger Bunk ◽  
Zhigang Yi ◽  
Thomas Behrendt ◽  
Dianming Wu ◽  
Meinrat Otto Andreae ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Forest Soils ◽  
Agricultural Soil ◽  
Carbonyl Sulfide ◽  
Soil Samples ◽  
Potential Contribution ◽  
Wide Range

Abstract. Carbonyl sulfide (OCS) is a chemically quite stable gas in the troposphere (lifetime ~ 2–6 years) and consequently some of it is transported up to the stratosphere where it contributes to the stratospheric sulfate layer. Due to the similarities in uptake mechanism between OCS and CO2, the use of OCS as a proxy for CO2 in ecosystem gross primary production (GPP) has been proposed. For this application a good understanding of uptake (UOCS) and production (POCS) processes of OCS in an ecosystem is required. A new OCS quantum cascade laser coupled with an automated soil chamber system enabled us to measure the soil-atmosphere OCS exchange of four different soil samples with high precision. The adjustment of the chamber air to different OCS mixing ratios (50, 500, and 1000 ppt) allowed us to separate production and consumption processes and to estimate compensation points (CPs) for the OCS exchange. At an atmospheric mixing ratio of 1000 ppt, the maximum UOCS was of the order of 22 to 110 pmol g−1 h−1 for needle forest soil samples and of the order of 3 to 5 pmol g−1 h−1 for an agricultural mineral soil, both measured at moderate soil moisture. Uptake processes (UOCS) were dominant at all soil moistures for the forest soils, while POCS exceeded UOCS at higher soil moistures for the agricultural soil, resulting in net emission. Hence, our results indicate that in (spruce) forests UOCS might be the dominant process, while in agricultural soils POCS at higher soil moisture and UOCS under moderate soil moisture seem to dominate the OCS exchange. The OCS compensation points (CPs) were highly dependent on soil water content and extended over a wide range of 130 ppt to 1600 ppt for the forest soils and 450 ppt to 5500 ppt for the agricultural soil. The strong dependency between soil water content and the compensation point value must be taken into account for all further analyses. The lowest CPs were found at about 20 % water filled pore space (WFPSlab), implying the maximum of UOCS under these soil moisture conditions and excluding OCS emission under such conditions. We discuss our results in view of other studies about compensation points and the potential contribution of microbial groups.

scholarly journals Soil water content in southern England derived from a cosmic-ray soil moisture observing system - COSMOS-UK

2016 ◽  
Vol 30 (26) ◽  
pp. 4987-4999 ◽  
Author(s):  
J. G. Evans ◽  
H. C. Ward ◽  
J. R. Blake ◽  
E. J. Hewitt ◽  
R. Morrison ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Southern England

Laboratory calibration of different soil moisture sensors in various soil types

2020 ◽  
Author(s):  
Urša Pečan ◽  
Damijana Kastelec ◽  
Marina Pintar
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Bulk Density ◽  
Soil Samples ◽  
Soil Types ◽  
Soil Moisture Sensors ◽  
Dry Soil

<p>Measurements of soil water content are particularly useful for irrigation scheduling. In optimal conditions, field data are obtained through a dense grid of soil moisture sensors. Most of the currently used sensors for soil water content measurements, measure relative permittivity, a variable which is mostly dependant on water content in the soil. Spatial variability of soil characteristics, such as soil texture and mineralogy, organic matter content, dry soil bulk density and electric conductivity can also alter measurements with dielectric sensors. So the question arises, whether there is a need for a soil specific calibration of such sensors and is it dependant on the type of sensor? This study evaluated the performance of three soil water content sensors (SM150T, Delta-T Devices Ltd, UK; TRIME-Pico 32, IMKO micromodultechnik GmbH, DE; MVZ 100, Eltratec trade, production and services d.o.o., SI) in nine different soil types in laboratory conditions. Our calibration approach was based on calibration procedure developed for undisturbed soil samples (Holzman et al., 2017). Due to possible micro location variability of soil properties, we used disturbed and homogenized soil samples, which were packed to its original dry soil bulk density. We developed soil specific calibration functions for each sensor and soil type. They ranged from linear to 5<sup>th</sup> order polynomial. We calculated relative and actual differences in sensor derived and gravimetrically determined volumetric soil water content, to evaluate the errors of soil water content measured by sensors which were not calibrated for soil specific characteristics. We observed differences in performance of different sensor types in various soil types. Our results showed measurements conducted with SM150T sensors were within the range of manufacturer specified measuring error in three soil types for which calibration is not necessary but still advisable for improving data quality. In all other cases, soil specific calibration is required to obtain relevant soil moisture data in the field.</p>

Monitoring soil water content at a heterogeneous oil sand reclamation site using a cosmic-ray soil moisture probe

2016 ◽  
Vol 543 ◽  
pp. 510-522 ◽  
Author(s):  
Mark J.P. Sigouin ◽  
Miles Dyck ◽  
Bing Cheng Si ◽  
Wei Hu
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Oil Sand

scholarly journals On the use of AMSU-based products for the description of soil water content at basin scale

2011 ◽  
Vol 15 (9) ◽  
pp. 2839-2852 ◽  
Author(s):  
S. Manfreda ◽  
T. Lacava ◽  
B. Onorati ◽  
N. Pergola ◽  
M. Di Leo ◽  
...  
Keyword(s):  
Time Series ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Land Surface ◽  
Skin Surface ◽  
Soil Moisture Dynamics ◽  
Basin Scale ◽  
Moisture Dynamics

Abstract. Characterizing the dynamics of soil moisture fields is a key issue in hydrology, offering a strategy to improve our understanding of complex climate-soil-vegetation interactions. Besides in-situ measurements and hydrological models, soil moisture dynamics can be inferred by analyzing data acquired by sensors on board of airborne and/or satellite platforms. In this work, we investigated the use of the National Oceanic and Atmospheric Administration – Advanced Microwave Sounding Unit-A (NOAA-AMSU-A) radiometer for the remote characterization of soil water content. To this aim, a field measurement campaign, lasted about three months (3 March 2010–18 May 2010), was carried out using a portable time-domain reflectometer (TDR) to get soil water content measures over five different locations within an experimental basin of 32.5 km2, located in the South of Italy. In detail, soil moisture measurements were carried out systematically at the times of satellite overpasses, over two square areas of 400 m2, a triangular area of 200 m2 and two transects of 60 and 170 m, respectively. Each monitored site is characterized by different land covers and soil textures, to account for spatial heterogeneity of land surface. Afterwards, a more extensive comparison (i.e. analyzing a 5 yr data time series) was made using soil moisture simulated by a hydrological model. Measured and modeled soil moisture data were compared with two AMSU-based indices: the Surface Wetness Index (SWI) and the Soil Wetness Variation Index (SWVI). Both time series of indices have been filtered by means of an exponential filter to account for the fact that microwave sensors only provide information at the skin surface. This allowed to understand the ability of each satellite-based index to account for soil moisture dynamics and to understand its performances under different conditions. As a general remark, the comparison shows a higher ability of the filtered SWI to describe the general trend of soil moisture, while the SWVI can capture soil moisture variations with a precision that increases at the higher values of SWVI.

Evaluation of NMR and other soil water content measurement methods at the point and field scale

2020 ◽  
Author(s):  
Matteo Bauckholt ◽  
Marco Pohle ◽  
Martin Schrön ◽  
Steffen Zacharias ◽  
Solveig Landmark ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Column ◽  
Cosmic Ray ◽  
Time Domain Reflectometry ◽  
Measurement Methods ◽  
Hydrogen Atoms ◽  
Conventional Methods

<p>Soil water content in the unsaturated zone is a key parameter of the environmental system. The understanding of soil moisture plays a major role with regard to questions of water and nutrient supply to plants, groundwater recharge, soil genesis and climatic interactions.</p><p>In our study we aim to test a new technology for the non-invasive measurement of soil moisture profiles, the so-called Surface-NMR (Nuclear Magnetic Resonance). The instrument applies magnetic fields to the ground and detects its changes caused by mobile and immobile hydrogen atoms in the soil column. Using four different frequencies, the data may provide insights into the water content of four distinct soil layers between the surface and 20 cm depth.</p><p>We carried out multiple NMR measurements at four different field sites in Germany and compared the data with conventional methods, such as gravimetric soil samples, Time Domain Reflectometry (TDR), and Cosmic-Ray Neutron Sensing (CRNS).</p><p>The dataset will be used to investigate the following research questions:</p><ol><li>Is the Surface-NMR method suitable to provide depth-resolved information of soil moisture under field conditions?</li> <li>Does Surface-NMR have the potential to replace or complement conventional methods of soil moisture measurement in the field?</li> <li>What can we learn about the spatial variability and scale dependency of soil moisture by combining three measurement methods of different scale (TDR, NMR, CRNS)?</li> </ol>

scholarly journals Spatio-temporal soil moisture retrieval at the catchment scale using a dense network of cosmic-ray neutron sensors

2021 ◽  
Vol 25 (9) ◽  
pp. 4807-4824
Author(s):  
Maik Heistermann ◽  
Till Francke ◽  
Martin Schrön ◽  
Sascha E. Oswald
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Root Zone ◽  
Cosmic Ray ◽  
Dense Network ◽  
Constrained Interpolation ◽  
Neutron Count ◽  
Spatio Temporal

Abstract. Cosmic-ray neutron sensing (CRNS) is a powerful technique for retrieving representative estimates of soil water content at a horizontal scale of hectometres (the “field scale”) and depths of tens of centimetres (“the root zone”). This study demonstrates the potential of the CRNS technique to obtain spatio-temporal patterns of soil moisture beyond the integrated volume from isolated CRNS footprints. We use data from an observational campaign carried out between May and July 2019 that featured a dense network of more than 20 neutron detectors with partly overlapping footprints in an area that exhibits pronounced soil moisture gradients within one square kilometre. The present study is the first to combine these observations in order to represent the heterogeneity of soil water content at the sub-footprint scale as well as between the CRNS stations. First, we apply a state-of-the-art procedure to correct the observed neutron count rates for static effects (heterogeneity in space, e.g. soil organic matter) and dynamic effects (heterogeneity in time, e.g. barometric pressure). Based on the homogenized neutron data, we investigate the robustness of a calibration approach that uses a single calibration parameter across all CRNS stations. Finally, we benchmark two different interpolation techniques for obtaining spatio-temporal representations of soil moisture: first, ordinary Kriging with a fixed range; second, spatial interpolation complemented by geophysical inversion (“constrained interpolation”). To that end, we optimize the parameters of a geostatistical interpolation model so that the error in the forward-simulated neutron count rates is minimized, and suggest a heuristic forward operator to make the optimization problem computationally feasible. Comparison with independent measurements from a cluster of soil moisture sensors (SoilNet) shows that the constrained interpolation approach is superior for representing horizontal soil moisture gradients at the hectometre scale. The study demonstrates how a CRNS network can be used to generate coherent, consistent, and continuous soil moisture patterns that could be used to validate hydrological models or remote sensing products.

scholarly journals Spatio-temporal soil moisture retrieval at the catchment-scale using a dense network of cosmic-ray neutron sensors

2021 ◽  
Author(s):  
Maik Heistermann ◽  
Till Francke ◽  
Martin Schrön ◽  
Sascha E. Oswald
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Ordinary Kriging ◽  
Cosmic Ray ◽  
Constrained Interpolation ◽  
Neutron Count ◽  
Moisture Variation ◽  
Spatio Temporal

Abstract. The method of Cosmic-Ray Neutron Sensing (CRNS) is a powerful technique to retrieve representative estimates of soil water content at a horizontal scale of hectometers (the field scale) and depths of tens of centimeters (the root zone). This study demonstrates the potential of the CRNS technique to obtain spatio-temporal patterns of soil moisture beyond the integrated volume from isolated CRNS footprints. We use data from an observational campaign between May and July 2019 which featured a network of more than 20 neutron detectors with partly overlapping footprints in an area that exhibits pronounced soil moisture gradients within 1 km2. The present study is the first to combine these observations in order to represent the heterogeneity of soil water content at the sub-footprint scale as well as between the CRNS stations. First, we apply a state-of-the-art procedure to correct the observed neutron count rates for static effects such as sensor sensitivity, vegetation biomass, soil organic carbon and lattice water, as well as for the influence of the temporally dynamic factors barometric pressure, air humidity, and incoming flux of neutrons. Based on the homogenised neutron data, we investigate the robustness of a uniform calibration approach using one calibration parameter value across all CRNS stations. Finally, we benchmark two different interpolation techniques in order to obtain space-time representations of soil moisture: first, Ordinary Kriging with a fixed range; second, a heuristic approach that complements the concept of spatial interpolation by the idea of a geophysical inversion (constrained interpolation). For the latter, we define a geostatistical model of the spatial soil moisture variation in the study area, and then optimize the parameters of that model so that the error of the forward-simulated neutron count rates is minimized. In order to make the optimization problem computationally feasible, we use a heuristic forward operator that is based on the physics of horizontal sensitivity of the neutron detector. The comparison with independent measurements from a cluster of soil moisture sensors (SoilNet) shows that the constrained interpolation approach outperforms Ordinary Kriging by putting a stronger emphasis on horizontal soil moisture gradients at the hectometer scale. The study demonstrates how a CRNS network can be used to generate consistent interpolated soil moisture patterns that could be used to validate hydrological models or remote sensing products.

Sign in / Sign up

Export Citation Format

Share Document