Soil Properties of Steep Appalachian Old Fields

Abstract

Shifting cultivation of corn (Zea mays) was widely practiced on steep, mesic slopes in the Appalachian Mountains during the period 1800—1930. Contemporary reports often emphasized both the severity of erosion during the period of cultivation, and the rapidity of reforestation following abandonment of agriculture. In eastern Kentucky, old fields that originated during this period are presently occupied by nearly pure yellow—poplar (Liriodendron tulipifera) stands that contrast with the mixed mesophytic forests found on areas that have never been cultivated. Soil properties on four ol1d fields °60 yr after abandonment were compared with those on uncultivated areas that were similar in physiography, geology, and, apparently, in original soils and vegetation. This paired—plot comparison examined the effect of both past land use and present vegetation on soil properties. Intensive sampling of the 0—60 cm soil depth revealed only minor differences in the properties of the formerly cultivated vs. uncultivated soils. Significantly higher concentrations of coarse fragments (particles > 2 mm) in the 0—5 cm depth of cultivated soils were attributed to the erosion of °2 cm (100 Mg/ha) of fine earth (particles <2 mm) and the subsequent burial of the coarse lag material. Significantly lower concentrations of available phosphorus in the 0—40 cm depth of cultivated soils, averaging 1 mg/kg less than in uncultivated soils, may have resulted from depletion during cultivation or from differential retention in the aboveground biomass following reforestation. Exchangeable calcium concentrations and pH of cultivated soils were significantly higher in the 0—10 cm and 0—60 cm depths, respectively, compared with uncultivated soils. Average plot values of exchangeable calcium and L. tulipifera basal area were linearly related (r2 = 0.87), as were the average values of these two variables over a downslope composition gradient on uncultivated areas (r2 = 0.78). These relationships, together with the greater content of calcium in the 0—60 cm depth of cultivated vs. uncultivated soils, suggested that relatively large amounts of calciums were accumulated in the surface soil as a result of the nutrient—cycling characteristics of the L. tulipifera—dominated old—field community. Fields cleared during the episode of shifting cultivation were typically located on landscape positions characterized by favorable water regimes, and by deep, porous soils with uniform physical properties throughout the rooting depth. Surface soils on such sites are resistant to permanent erosional degradation, and are rapidly rejuvenated by processes associated with reforestation. Thus the effects of both past land use and present vegetation on the properties of these soils are for the most part superficial and ephemeral.