Wednesday, November 15, 2006 - 10:00 AM

Impact of Coarse Fragments on Carbon and Nutrient Pools in Forest Soils of the Appalachians.

Mary P. Parrish and Thomas R. Fox. Virginia Tech, Dept of Forestry, PO Box 7866, Charleston, WV 25356

This study was initiated to investigate the edaphic factors related to site quality  in the southern and central Appalachians.   Because many of the soils in the Appalachians contain large quantities of coarse fragments, the focus of the study was to quantify their impact on nutrient and  carbon content of these soils. Seven sites in Virginia and West Virginia were selected for study. Quantitative soil pits were excavated to 1m or the depth of bedrock by pedogenic horizon.  Coarse fragment content of each horizon was determined. Samples of the fine soil fraction (< 2 mm) and the coarse fragments in the following size classes: 2-5 mm; 5-9 mm; 9-19 mm, 19-76 mm; and > 76 mm were collected and returned the lab for analysis. Fine fraction bulk density and coarse fragment density and volume were determined.   Total C and N and Mehlich III extractable P, K, and Ca were determined on the fine fraction and the coarse fragments.  Total pools of C, N, P, K, and Ca including the fine fraction and the coarse fractions were determined for each soil by pedogenic horizon and summed through the entire profile. The results  indicate the importance of including coarse fragments into estimates of carbon and nutrient pools in these Appalachian soils. Ignoring the contribution of coarse fragments would cause total C and N pools to be underestimated by up to 58%; extractable P pools to be underestimated by 20 to 70%, extractable K pools by 5 to 64%; and extractable Ca pools by 60 to 90%.  The importance of sampling beyond the A horizon was also evident.  In all soils, C, N, and extractable P, K, and Ca contents were all greater in the B horizons than in the A horizon.