A simple and cost-effective method for cable root detection and extension measurement in estuary wetland forests

This work presents the development of a low-cost method to measure the length cable roots of black mangrove (Avicennia germinans) trees to define the boundaries of central part of the anchoring root system (CPRS) without the need to fully expose root systems. The method was tested to locate and measure the length shallow woody root systems. An ultrasonic Doppler fetal monitor (UD) and a stock of steel rods (SR) were used to probe root locations without removing sediments from the surface, measure their length and estimate root-soil plate dimensions. The method was validated by comparing measurements with root lengths taken through direct measurement of excavated cable roots and from root-soil plate radii (exposed root-soil material when a tree tips over) of five up-rooted trees with stem diameters (D130) ranging between 10 and 50 cm. The mean CPRS radius estimated with the use of the Doppler was directly correlated with tree stem diameter and was not significantly different from the root-soil plate mean radius measured from up-rooted trees or from CPRS approximated by digging trenches. Our method proved to be effective and reliable in following cable roots for large amounts of trees of both black and white mangrove trees. In a period of 40 days of work, three people were capable of measuring 648 roots belonging to 81 trees, out of which 37% were found grafted to other tree roots. This simple method can be helpful in following shallow root systems with minimal impact and help map root connection networks of grafted trees

Forestry applications of ground-penetrating radar

Ground-penetrating radar (GPR) is a geophysical and close-range remote sensing technique based on the use of radar pulses to obtain cross-section images of underground features. This method is characterized by the transmission of an electromagnetic short length pulse (1-2 ns), presenting a centre frequency ranging from 10 MHz to 2.5 GHz. The principles of GPR operation are based on the ability of low frequency radar waves to penetrate into a non-conductive medium, usually subsoil, but also walls, concrete or wood. Those waves are detected after suffering a reflection in electromagnetic discontinuities of the propagation medium. Therefore, this is a suitable method to study changes in those physical properties, and also to characterize different mediums and the reflective targets providing information about their physical properties. The aim of this work is to describe and demonstrate different applications of GPR in forestry, showing the obtained results together with their interpretation. Firstly, in this paper, it is illustrated how GPR is able to map shallow bedrock, subsoil stratigraphy and also to estimate shallow watertable depth. Secondly, different tree trunks as well as dry timber are analyzed, evaluating the different radar data obtained in each particular case, and observing differences in their electromagnetic properties related to the GPR response. Finally, several measurements were taken in order to analyze the use of GPR to detect tree root systems using polarimetric techniques, being possible to detect medium and big size roots, together with groups of small roots. Key words: GPR, remote sensing, bedrock, watertable, trunk, root system.Postprint (published version

Mapping and assessment of tree roots using ground penetrating radar with low-cost GPS

In this paper, we have presented a methodology combining ground penetrating radar (GPR) and a low-cost GPS receiver for three-dimensional detection of tree roots. This research aims to provide an effective and affordable testing tool to assess the root system of a number of trees. For this purpose, a low-cost GPS receiver was used, which recorded the approximate position of each GPR track, collected with a 500 MHz RAMAC shielded antenna. A dedicated post-processing methodology based on the precise position of the satellite data, satellite clock offsets data, and a local reference Global Navigation Satellite System (GNSS) Earth Observation Network System (GEONET) Station close to the survey site was developed. Firstly, the positioning information of local GEONET stations was used to filter out the errors caused by satellite position error, satellite clock offset, and ionosphere. In addition, the advanced Kalman filter was designed to minimise receiver offset and the multipath error, in order to obtain a high precision position of each GPR track. Kirchhoff migration considering near-field effect was used to identify the three-dimensional distribution of the root. In a later stage, a novel processing scheme was used to detect and clearly map the coarse roots of the investigated tree. A successful case study is proposed, which supports the following premise: the current scheme is an affordable and accurate mapping method of the root system architecture

Effects of 11 Years of CO2 Enrichment on Root Biomass and Spatial Distribution in a Florida Scrub-Oak Ecosystem

A Florida (USA) scrub-oak ecosystem was exposed to elevated atmospheric CO2 in open-top chambers from 1996-2007. Minirhizotrons and ground-penetrating radar (GPR) were used to measure fine root (\u3c 2 mm diameter) and coarse root (\u3e 5 mm diameter) biomass, respectively. After 11 years of CO2 enrichment, there was a trend of greater total root biomass under elevated CO2. Fine root biomass exhibited a pattern of recovery and steady state throughout the study, with significant CO2 stimulation observed only after disturbance. Greater root biomass under elevated CO2 during recovery periods could result in greater carbon inputs belowground, alteration of the soil carbon cycle, and faster ecosystem recovery. At the end of the study, a greater proportion of fine root biomass was found deeper in the soil in plots exposed to elevated CO2. The shift of biomass deeper in the soil and pattern of recovery and steady state suggest a limit on the soils\u27 capacity to support fine roots. The dominant plants were not limited by water or nutrients, indicating that root responses to CO2 enrichment were likely constrained by soil resource space

Experimental Evaluation of Several Key Factors Affecting Root Biomass Estimation by 1500 MHz Ground-Penetrating Radar

Accurate quantification of coarse roots without disturbance represents a gap in our understanding of belowground ecology. Ground penetrating radar (GPR) has shown significant promise for coarse root detection and measurement, however root orientation relative to scanning transect direction, the difficulty identifying dead root mass, and the effects of root shadowing are all key factors affecting biomass estimation that require additional research. Specifically, many aspects of GPR applicability for coarse root measurement have not been tested with a full range of antenna frequencies. We tested the effects of multiple scanning directions, root crossover, and root versus soil moisture content in a sand-hill mixed oak community using a 1500 MHz antenna, which provides higher resolution than the oft used 900 MHz antenna. Combining four scanning directions produced a significant relationship between GPR signal reflectance and coarse root biomass (R2 = 0.75) (p \u3c 0.01) and reduced variability encountered when fewer scanning directions were used. Additionally, significantly fewer roots were correctly identified when their moisture content was allowed to equalize with the surrounding soil (p \u3c 0.01), providing evidence to support assertions that GPR cannot reliably identify dead root mass. The 1500 MHz antenna was able to identify roots in close proximity of each other as well as roots shadowed beneath shallower roots, providing higher precision than a 900 MHz antenna. As expected, using a 1500 MHz antenna eliminates some of the deficiency in precision observed in studies that utilized lower frequency antennas

Crop Phenotyping of Sorghum bicolors Physiological Response to Salt-Affected Soils Using TLS and GPR Remote Sensing Technologies in Nevada Drylands

Saline and sodic soils are major abiotic stressors on the production of flood-irrigated crops in drylands. We conducted a crop phenotyping, remote sensing study on five genotypes of sorghum [Sorghum bicolor (L.) Moench], a drought and salt-tolerant crop, to assist in the molecular breeding of salt-tolerant cultivars. A control plot and a spatially heterogeneous saline-sodic plot (treatment plot) were established in collaboration with Dr. Yerka, Mr. Alfredo Delgado, Dr. Washington-Allen, the Nevada Agricultural Experiment Station (NAES) and the United States Department of Agriculture’s Plant Materials Center (USDA-PMC) in Fallon, Nevada. This location is representative of the variable salinity/sodicity conditions typical of Northern Nevada soils and associated belowground biomass dynamics in drylands. We generated pre- and post-harvest soil attribute maps of the treatment plot using spatial interpolation, we expected individual genotypes to be affected differently by the gradient of various soil constituents. We hypothesized that above- and belowground three-dimensional structural phenology of the five genotypes would be differently affected across the salinity gradient in the treatment plot relative to the control plot. Additionally, we hypothesized that the GPR signal return would vary with the salinity gradient. Finally, we expected an increase in belowground biomass, relative to the control plot, in response to salt-stress as an adaptation to drought. The phenology of coarse-root depth and three-dimensional structure from pre-planting to harvest was non-invasively measured 15 times using a real-time kinematic (RTK) GPS-mounted IDS GeoRadar dual channel (400MHz and 900MHz) ground penetrating radar (GPR) system. Plant height and three-dimensional structural phenology of the five varieties were mapped using a FARO Focus3D X 330 terrestrial laser scanner (TLS). We found differences in above- and belowground three-dimensional structural phenology across the five genotypes in response to the salinity and sodicity gradient. Of the five genotypes in this study, only four emerged in the treatment plot, where Richardson Seed’s Ultra-Early Hybrid performed best under the gradient of salinity and sodicity with the highest rate of emergence (68%), the highest rate of panicle production (4.1 panicles per row), and the greatest panicle volume (67.2%) relative to the control plot. Furthermore, we found that the GPR return signal was not able to detect root mass in the highly saline-sodic soil, however, I was able to detect root mass phenology in the control plot. GPR return signal was not linear in response to the salinity gradient, however, a signal pattern emerged from the different salinity ranges suggesting a gradient response. This study shows the efficacy of the use of these technologies in crop phenotyping and precision agriculture. Future work may improve TLS derived data processing efficiency by developing methods for automating the detection of phenotypic traits (e.g., panicles, leaf area index, number of individual plants). These methods likely will include machine learning algorithms, allometric equations for biomass calculations, and use of drone-mounted LiDAR to reduce occlusion. The use of GPR in the salt-affected soils of this study was not able to definitively identify root mass, however, its use in soil composition for salts and other constituents is indeed promising. Further testing of GPR’s non-detect threshold in salt-affected soils and its ability to quantify individual soil constituents has potential to be highly valuable to the field of soil science and precision agriculture. Furthermore, this study was able to detect a root mass response using GPR, future work may focus on differentiating genotypic variation in root phenology

An enhanced data processing framework for mapping tree root systems using ground penetrating radar

The preservation of natural assets is nowadays an essential commitment. In this regard, root systems are endangered by fungal diseases which can undermine the health and stability of trees. Within this framework, Ground Penetrating Radar (GPR) is emerging as a reliable non-destructive method for root investigation. A coherent GPR-based root-detection framework is presented in this paper. The proposed methodology is a multi-stage data analysis system that is applied to semi-circular measurements collected around the investigated tree. In the first step, the raw data are processed by applying several standard and advanced signal processing techniques, to reduce noise-related information. In the second stage, the presence of any discontinuity element within the survey area is investigated by analysing the signal reflectivity. Then, a tracking algorithm aimed at identifying patterns compatible with tree roots is implemented. Finally, the mass density of roots is estimated by means of continuous functions, to achieve a more realistic representation of the root paths and to identify their length in a continuous and more realistic domain. The method was validated in a case study in London (UK), where the root system of a real tree was surveyed using GPR and a soil test pit was excavated for validation purposes. Results support the feasibility of the data processing framework implemented in this study

Coarse Root Biomass and Architecture: Applications of Ground Penetrating Radar

The effectiveness of ground penetrating radar (GPR) to identify and quantify coarse roots was tested in a mixed-oak forest in Southeastern Virginia using experimental pits and locally excavated root segments. GPR was found to be highly dependent on low soil moisture levels as it is unable to differentiate root structures if they possess similar moisture content as their surrounding soil. Likewise, GPR was unable to identify simulated dead roots. This does not alter the effectiveness of GPR to measure living coarse root biomass, but does present the potential for underestimation of carbon storage in coarse root structures, as a dead roots continue to store carbon. GPR was able to recognize and quantify increasing root density suggesting an ability to quantify change in root mass over time, but it was not able to reliably represent changes in root diameter. Coarse root biomass estimation using GPR was conducted using a grid scanning technique applied to sample plots located within multiple systems. GPR effectively measured coarse root biomass across multiple systems, showing no significant difference between estimated and observed coarse root biomass in a Virginia mixed-oak forest ecosystem, a Florida scrub-oak ecosystem, or a Florida longleaf pine flatwoods ecosystem. GPR appears to have difficulty with root structures near the surface, as it is not able to reliably separate these structures from the soil-air interface. Post-experimental disturbance effects were examined in a Florida scrub-oak ecosystem, following an 11-year open-top chamber elevated CO2 experiment that concluded in 2006 and had been abandoned for seven years. Aboveground harvest showed a significantly higher regrowth two years post fire in previously elevated CO2 plots when compared with plots that were kept at ambient CO2 levels throughout the duration of the original experiment. No significant difference was found in coarse root biomass between the two treatments; however, a non-significant trend of 12% higher biomass in the previously elevated CO2 plots was found that coincided with a similar trend observed during the original experiment. Long-lasting effects of elevated CO2 appear to exist within this system, indicating an ability for plants to store additional carbon and to regrow more rapidly following fire disturbance. Carbon storage within coarse roots was examined in a Florida longleaf pine flatwoods ecosystem as part of a larger, ongoing effort to quantify total carbon storage and flux within multiple systems relative to longleaf pine restoration. Coarse root carbon storage was estimated at 3.5 – 3.7 kg C/m2, suggesting large carbon storage potential associated with longleaf pine restoration. GPR is an effective, non-destructive tool for quantifying coarse root biomass and an effective but limited tool for determining root architecture. Both applications of GPR are highly dependent on user-determined settings during data collection and post-collection processing, thus effective GPR application is highly dependent on the level of familiarity possessed by the operator

Variabilita zásob uhlíku v půdě a možnost využití GPR radaru k jejich zjišťování

In the context of ongoing climate change, more attention is being given to soil and its organic carbon pool. This is because soil could partially compensate for the increasing amount of carbon dioxide in the atmosphere or, on the other hand, be a vast pool of carbon dioxide if organic matter stored in soil mineralizes. Therefore, the precision of soil organic carbon pool estimation, development of monitoring methods, and revelation of factors controlling the pool have been more and more focused on by soil scientists. Conventional soil sampling for soil organic carbon pool estimation and modelling includes manual sampling, measuring forest floor depth and bulk density, and taking soil samples for carbon concentration analysis. These are time and labour demanding. Therefore, there is an effort to develop precise models predicting the carbon pool based on its driving factors that would limit the amount of fieldwork. The models often use remote sensing data, and, in addition, there is an effort to estimate soil organic carbon concentration from soil spectral characteristics. Nevertheless, another variable needed to estimate the organic carbon pool is the thickness of the soil profile or individual soil horizons. The thickness can hardly be determined from remote sensing data, so it has to be measured...V souvislosti s probíhající klimatickou změnou zapříčiněnou zejména růstem oxidu uhličitého v atmosféře, je stále více pozornosti věnováno výpočtu organického uhlíku v půdě a možnostem jeho sekvestrace. Půda je největším terestrickým zásobníkem uhlíku a může zpomalovat stoupající množství oxidu uhličitého v atmosféře jeho sekvestrací nebo v opačném případě být významným zdroje oxidu uhličitého, pokud by došlo k mineralizaci organického uhlíku uloženého v půdě. Proto se pedologie stale více zabývá zpřesňováním odhadů uhlíkových zásob, vývojem metod jejich monitorování a hledáním faktorů, které sekvestraci a stabilizaci uhlíku v půdě ovlivňují. Konvenční sběr dat za účelem odhadů zásob uhlíku v půdě sestává z manuálního terénního průzkumu pomocí půdních sond, měření mocností horizontů a odběru vzorků pro stanovení obsahu organického uhlíku. Tyto práce jsou však časově i finančně značně náročné. Proto je snahou nalézt faktory, které zásobu organického uhlíku ovlivňují a na jejich základě predikovat množství uhlíku v místech, kde půdní průzkum nebyl proveden. Významný posun přinesl i dálkový průzkum země, který umožňuje odhadovat koncentraci půdního organického uhlíku na základě spektrální odrazivosti půdy. Nicméně, jedním z klíčových parametrů potřebných pro odhad zásob uhlíku v půdě je mocnost...Department of Physical Geography and GeoecologyKatedra fyzické geografie a geoekologiePřírodovědecká fakultaFaculty of Scienc

Recent advances in tree root mapping and assessment using non-destructive testing methods: a focus on ground penetrating radar

This paper provides an overview of the existing literature on the subject of assessment and monitoring of tree roots and their interaction with the soil. An overview of tree root systems architecture is given, and the main issues in terms of health and stability of trees, as well as the impact of trees on the built environment, are discussed. An overview of the main destructive and non-destructive testing (NDT) methods is therefore given. The paper also highlights the lack of available research based outputs in the field of tree roots and soil interaction, as well as of the interconnectivity of tree roots with one another. Additionally, the effectiveness of non-destructive methods is demonstrated, in particular ground penetrating radar, in mapping tree root configurations and their interconnectivity. Furthermore, the paper references recent developments in estimating tree root mass density and health