ERODED AGGREGATE SIZE DISTRIBUTIONS FROM DISTURBED LANDS

A characterization of eroded soil properties, especially size, is requ ired for proper usage of modern process-based soil erosion models. In a study addressing reclaimed mine land erodibility, over 350 measured eroded aggregate size distributions were collected from erosion plots created on reclaimed and nearby unmined soils at three separate strip mine sites. The experimental design allowed for a comparison of eroded aggregate size distributions as a function of land slope, run sequenc e, and reclamation treatment. No influence of slope was apparent, as d istributions collected from plots constructed at 6% slope were coarser than those collected from 18% slope, but finer than those collected f rom 12%. Samples collected during extra inflow runs, in which runoff r ates, flow velocity, and rill erosion were greatest, had coarser distr ibutions than samples collected during rainfall only runs, which tende d to have similar distributions. Distributions from reclaimed topsoil treatments were similar to nearby unmined soils and were distinct from subsoil reclamation treatments. At two sires, topsoil treatments had coarser distributions, while the converse was true at the third. Distr ibutions taken from topsoil and unmined soil treatments were used to d evelop five regression equations to predict the percentage of total er oded soil mass falling into each of five size classes-clay, silt, and three sand sizes. A stepwise, multivariate regression technique was us ed to select the best independent variables from 30 soil parameters. I ndependent variables that proved to be significant in at least one equ ation include primary particle and water stable aggregate size distrib utions, bulk density, organic carbon, and soil moisture. The number of significant independent variables ranges from II to 15 and correlatio n coefficients (R(2)) range from 0.77 to 0.53, which is a general impr ovement over previously published prediction methods.