Properties and acid risk assessment of soils in two parts of the Cherry River Watershed, West Virginia.

Abstract:

Declining forest health and decreasing species diversity have been observed during the past several decades across North America and Europe, and some of this decline has been attributed to acid deposition. Decreases in soil pH and increases in soil acidity and the Ca:Al ratios are indicators of the risk of forest decline due to acid inputs and aluminum toxicity. The Cherry River watershed, which lies within the Monongahela National Forest in West Virginia, has some of the highest rates of acid deposition in Appalachia, with a gradient of increasing acid loads from west to east in the watershed.

Streams on the western side have an average pH of 5.8 and acid neutralizing capacity (ANC) of 20 mg L -1 as CaCO 3, while eastern side streams show an average pH of 4.7 and ANC of -55 mg L -1 as CaCO 3. The eastern side also has a greater percentage of acidic parent material from Pottsville geology than the western side. In this study, we determined soil physical and chemical properties of these western and eastern areas within the Cherry River watershed and assessed risk of forest regeneration failure based on acid soil indicators.

East area soils had an average pH of 3.9 compared to 4.2 for West area soils. Aluminum and iron concentrations were also higher in East vs West soils, which translated into slightly lower Ca:Al ratios in East area soils. Results showed that 75% of the sampled soils in the East area had a 95% to 100% risk of forest decline compared to 52% in the West area. These high degrees of risk mean there is a high probability of regeneration failure and forest decline after conventional tree harvesting. Therefore, adjustments to forest management plans and harvesting techniques may be needed, as well as the possibility of implementing mitigation measures.

These may include changing harvesting procedures, lengthening rotations, leaving wood on site, or liming watershed soils. Without these adjustments or mitigation efforts after harvesting, the forest potentially will not regenerate a valuable timber stand to replace the one that was harvested and may result in changes to forest tree species composition and quality.