Soil Organic Carbon Variability by Aspect and Slope in the High Elevation Soils of the Southwest Virginia Mountains

Abstract

Limited information is available on carbon(C)sequestered in frigid Appalachian forest soils. However,the cool moist forests of the high elevations probably hold more C than any other mineral soils in Virginia. The objectives of the study were to determine the amount and variability of soil C across aspect and slope classes in a frigid temperature regime area of Tazewell County, VA. Soils were sampled to characterize two aspect classes, N(340-90º) and S (160-270º), and three slope classes, 7-15%, 15-35%, 35-55%. Organic (L,F,H) and mineral layers and horizons (upper 5cm, A, B) were sampled at each site. Whole soil (including organic and mineral horizons) C contents on N aspects (135 Mg/ ha) were greater than on south aspects (107 Mg/ha). Average whole soil C across all sites was 112 Mg ha-1. The A horizons on N aspects (13cm) were deeper than those of the S aspects (8 cm), while average leaf litter weights were greater on the S aspects (25 Mg/ ha) versus the N (17 Mg/ ha). B horizon C was greater than 1.5 % and made up more than half of the total soil C. Carbon increased with slope on N aspects, but did not increase with slope on S aspects, because estimated solar insolation potential decreases with increasing slope on N aspects and has no trend on S-facing slopes. Total C appears to be greatest on steep N-facing slopes because cooler and moister conditions promote better mixing of organic material into the mineral soil.