Saturday, 15 July 2006

Use of Ground-Penetrating Radar to Assess Soil Heterogeneity.

Eric Sucre and Thomas Fox. Virginia Tech Univ, 228 Cheatham Hall, Blacksburg, VA 24061

Forest Soils are heterogeneous by nature, complicates understanding nutrient cycling and nutrient availability of forest soils at a landscape level. One contributor of this is old stump holes, which are known to be zones high in organic matter, soil moisture, and nutrient availability. Roots, which are extremely plastic, have a tendency to migrate and concentrate around these nutrient pools. However, when sampling forest soils, these areas are thought to be anomalies and are often disregarded. The objectives of this study were to: (i) use ground-penetrating radar (GPR) to locate old stump holes left from either decaying or previously harvested trees, (ii) calculate approximate contribution of these areas in terms of the proportion of total bulk soil, and (iii) quantify changes in nutrient availability with distance away from stump holes. The study plots are part of the Silviculture and Biodiversity in Southern Appalachian Forests project. Six replications of no-treatment "control" plots were used; four of which were located in the George Washington and Jefferson National Forests in Virginia and two in the MeadWestvaco's Corporation's Wildlife and Ecosystem Research Forest in West Virginia. Nutrient availability was quantified by measuring available NH4+and NO3-, exchangeable cations of Mg2+, Ca2+, and K+, pH, soil organic matter, and soil moisture at specified depths (0-15 cm, 15-30 cm, and 30-50 cm). Results from this study seek to confirm the utility of GPR as a non-destructive sampling tool for forest managers to map zones of high nutrient availability and secondary root biomass. Long term goals of this study are to examine how growth of various understory and overstory species are effected by zones of high nutrient availability and how growth changes with distance away from these nutrient pools.

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