Thursday, November 16, 2006 - 10:15 AM
324-1
Influence of Soil Heterogeneity on Nutrient Availability.
Nutrient availability is extremely variable and is often scattered in patches across forested landscapes. These microsites vary due to differences in slope, aspect, underlying parent material, and climate. Decomposing stumps provide a rich medium for enhanced plant growth because of the relative increase in total organic matter, aeration, root penetrability and cation exchange capacity as well as a decrease in soil bulk density. The quantity of decomposing stumps in Southern Appalachian Hardwood forests is high and can comprise a significant portion of the total soil surface area. Furthermore, the vertical extent of these decomposing stumps provides an extension of the more nutrient rich O- and A-horizons. This study was comprised of three, 10m x 10m plots established at seven independent sites across three different physiographic regions in Virginia and West Virginia : 1) the Ridge and Valley, 2) Cumberland Plateau and 3) Alleghany Plateau. Comparisons of soil physical and chemical properties were conducted between areas directly influenced by decomposing stumps and those representing the surrounding bulk soil. Average soil depth was estimated using ground-penetrating radar (GPR) which works well in low clay, coarser textured soils often found in the Southern Appalachias. Root cores were extracted to quantify potential differences in total mass and quantity of fine roots between the two sampled areas, decomposing stumps and the bulk soil. Potentially mineralizable nitrogen (N) was determined via a 10-week incubation period. Cation exchange capacity and available phosphorus were also estimated. Volume estimates of the areas influenced by decomposed stumps were calculated using excavation techniques and nutrient concentration data were used to examine the contribution these microsites provide to total nutrient availability. Although the total area that these microsites comprise is small the relative concentration of available nutrients for immediate plant uptake is often significantly higher than the surrounding bulk soil.
Recorded presentation