Site Relations of Slash Pine on Dredge Mine Spoils

Abstract

AbstractDredge mining for heavy minerals is carried out on large areas of Spodosol soils in the Georgia‐Florida coastal plain. Attempts to return these areas to productive slash pine (Pinus elliottii Engelm. var. elliotii) forests have usually failed. This study was conducted to determine if changes in soil moisture regime or extremely low nutrient availability induced by the mining operation were the causes of such failure. Nutrient contents of the mined soils were low, but this did not appear to be the major cause of poor tree growth. Changes in topography and the removal of organic and sesquioxide coatings from the thick spodic horizon caused the mined soils' moisture regimes to be very different from those occurring in the coarse sandy soils prior to mining. Before mining, the soils were fairly uniform, somewhat poorly drained Spodosols. After mining, the soils ranged from Typic to Aquic Quartzipsamments, and only a small proportion of the area retained a moisture regime suitable for vigorous slash pine growth. Plantation failure on these sites could have been mitigated by grading the spoils to nearly level contours and increasing the organic matter content through additions of waste humate from the mining process or sewage sludge, or by planting a variety of tree species onto the various microsites present in the mined landscape.