Preliminary use of ground-penetrating radar and electrical resistivity tomography to study tree roots in pine forests and poplar plantations
Terenzio Zenone A B G , Gianfranco Morelli C , Maurizio Teobaldelli B , Federico Fischanger C , Marco Matteucci B , Matteo Sordini D , Alessio Armani C , Chiara Ferrè E , Tommaso Chiti F and Guenther Seufert BA Department of Forest Science and Environment, University of Tuscia, Viterbo, Italy.
B European Commission DG-Joint Research Centre, Institute for Environment and Sustainability, Climate Change Unit, T.P. 050 Via E. Fermi, I-21027 Ispra (Va), Italy.
C Geostudi Astier, Via della Padula, 165. 57125 Livorno, Italy.
D LAPETLAB, Landscape Archaeology and Remote Sensing Laboratory, University of Siena, Via Roma 56, 53100 Siena, Italy.
E DISAT, Department of Environmental Sciences, University of Milano-Bicocca, P.za della Scienza, 1 20 126 Milan, Italy.
F Department of Soil Science and Plant Nutrition, University of Florence, Piazzale delle Cascine, 16–50144 Firenze, Italy.
G Corresponding author. Email: terenzio.zenone@jrc.it
This paper originates from a presentation at the 5th International Workshop on Functional–Structural Plant Models, Napier, New Zealand, November 2007.
Functional Plant Biology 35(10) 1047-1058 https://doi.org/10.1071/FP08062
Submitted: 8 March 2008 Accepted: 4 August 2008 Published: 11 November 2008
Abstract
In this study, we assess the possibility of using ground penetrating radar (GPR) and electrical resistivity tomography (ERT) as indirect non-destructive techniques for root detection. Two experimental sites were investigated: a poplar plantation [mean height of plants 25.7 m, diameter at breast height (dbh) 33 cm] and a pinewood forest mainly composed of Pinus pinea L. and Pinus pinaster Ait. (mean height 17 m, dbh 29 cm). GPR measures were taken using antennas of 900 and 1500 MHz applied in square and circular grids. ERT was previously tested along 2-D lines, compared with GPR sections and direct observation of the roots, and then using a complete 3-D acquisition technique. Three-dimensional reconstructions using grids of electrodes centred and evenly spaced around the tree were used in all cases (poplar and pine), and repeated in different periods in the pine forest (April, June and September) to investigate the influence of water saturation on the results obtainable. The investigated roots systems were entirely excavated using AIR-SPADE Series 2000. In order to acquire morphological information on the root system, to be compared with the GPR and ERT, poplar and pine roots were scanned using a portable on ground scanning LIDAR. In test sections analysed around the poplar trees, GPR with a high frequency antenna proved to be able to detect roots with very small diameters and different angles, with the geometry of survey lines ruling the intensity of individual reflectors. The comparison between 3-D images of the extracted roots obtained with a laser scan data point cloud and the GPR profile proved the potential of high density 3-D GPR in mapping the entire system in unsaturated soil, with a preference for sandy and silty terrain, with problems arising when clay is predominant. Clutter produced by gravel and pebbles, mixed with the presence of roots, can also be sources of noise for the GPR signals. The work performed on the pine trees shows that the shape, distribution and volume of roots system, can be coupled to the 3-D electrical resistivity variation of the soil model map. Geophysical surveys can be a useful approach to root investigation in describing both the shape and behaviour of the roots in the subsoil.
Additional keywords: ERT, GPR, root biomass assessment, root detection.
Acknowledgements
This research was partly funded by the CarboEurope IP project (EU-Contract No. GOCE-CT-2003- 505572), FISR Carboitaly, and by the JRC-IES-CCU-Action 24002 – Greenhouse Gases in Agriculture, Forestry and Other Land Uses – GHG-AFOLU. We thank all colleagues of the Climate Change Units who helped us with the direct measurements.
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