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

SSSAJ: Volume 71: Number 4 • July–August 2007 Soil Sci. Soc. Am. J. 71:1314–1322 doi:10.2136/sssaj2006.0323 Received 12 Sept. 2006. *Corresponding author ([email protected]). © Soil Science Society of America 677 S. Segoe Rd. Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. The spatial variability of forest soils is an important factor for forest site planning, quality, and productivity (Schoenholtz et al., 2000). Forest soils serve multiple production and environmental functions and maintaining these functions is crucial for sustainable forest management. Accurate characterization of the soil is a preliminary step in site establishment, since both lateral and vertical soil heterogeneity may have an impact on tree growth patterns. Soil texture is a fundamental qualitative soil physical property, infl uencing many other properties and processes including soil formation, water movement, erosion potential, and cation exchange capacity (CEC). It strongly affects soil moisture and controls the pool of nutrients available for plant uptake (Mc Bride et al., 1990). Soil discontinuities may be defi ned by signifi cant changes in soil texture, and their identifi cation and spatial delineation is important in land use decision making (Ogg et al., 2000). The presence of a clay layer in a sandy soil constitutes a discontinuity that restricts infi ltration and infl uences the lateral movement of soil water and agrochemicals (Doolittle et al., 1994). Concerning forest productivity, Woolery et al. (2002) selected clay content in the B horizon as an important parameter for estimating species productivity. Also, Bravo and Montero (2001) found texture to be an important factor for forest productivity. Generally, soil texture is known to determine the impact of soil disturbances on tree growth (Gomez et al., 2002). A potential consequence of soil compaction caused by harvesting or site preparation is the signifi cant loss of site productivity. It should be mentioned, however, that forest productivity relies on the interplay of soil physical, chemical, and biological properties and processes, which can be complex and varying among forest ecosystems (Schoenholtz et al., 2000). Consequently, future forest management practices should be site specifi c and account for the spatial variability of soil properties. Therefore, knowledge of the spatial variability of soil texture may be important for interpreting tree productivity and planning forest management strategies. New techniques have evolved that allow soil spatial variability to be identifi ed using noninvasive, geophysical soil sensors. Sensors based on electromagnetic induction (EMI) have already proved their utility for soil characterization in agricultural soils (Corwin and Lesch, 2005). In this sensing technique, the bulk or apparent soil electrical conductivity (ECa) Using the EM38DD Soil Sensor to Delineate Clay Lenses in a Sandy Forest Soil