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Using the EM38DD Soil Sensor to Delineate Clay Lenses in a Sandy Forest Soil

^a Dep. of Soil Management and Soil Care, Ghent Univ., Coupure 653, 9000 Gent, Belgium
^b Research Institute for Nature and Forest, Gaverstraat 4, 9500 Geraardsbergen, Belgium

View larger version (31K): [in this window] [in a new window]   Fig. 1. Point ordinary kriging maps of electrical conductivity (a) using the horizontal orientation (EC_h, mS m–1) with measurement locations of EM38DD (dots) and (b) using the vertical orientation (EC_v, mS m–1) with locations of texture samples (squares), and (c) the profile ratio (PR). (Metric Lambert coordinates on x and y axes.)

View larger version (14K): [in this window] [in a new window]   Fig. 2. Mean clay content of the heterogeneous and homogeneous soil profiles, shown in layers of 0.5 m (error bars represent the standard deviation).

View larger version (18K): [in this window] [in a new window]   Fig. 3. (a) Fuzziness performance index (FPI) and normalized classification entropy (NCE) as a function of the number of classes, and (b) map of fuzzy classification of the profile ratio into five classes.

View larger version (35K): [in this window] [in a new window]   Fig. 4. Prediction of the clay lens according to (a) the fuzzy-k-means reclassification and (b) the indicator kriging probability map showing the probability that the profile ratio is 0.81.

View larger version (16K): [in this window] [in a new window]   Fig. 5. (a) Indicator variogram model of the validation data (dots with number of data pairs) and (b) the validation image.

View larger version (13K): [in this window] [in a new window]   Fig. 6. (a) The measure of the harmonic mean of precision and recall weighted at 0.5 (F0.5) in function of probability thresholds and (b) classification of the indicator kriging probability map (with a probability threshold of 0.50).

View larger version (17K): [in this window] [in a new window]   Fig. 7. (a) Scatterplot of electrical conductivity in the vertical orientation (EC_v) vs. the depth of the clay lens (Dc), and (b) the depth of the textural discontinuity (clay lens in meters below the surface and metric Lambert coordinates on x and y axes).