2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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600 SENCINDIVER & AMMONS IX. HORIZON FORMATION A horizons may develop in minesoils within 5 yr (Daniels & Amos, 1981; DeMent et al., 1992; Haering et al., 1993; Roberts et al., 1988a,b; Schafer et al., 1980; Thomas & Jansen, 1985; Varela, 1993). These young A horizons may be thin ( <13 cm thick) but several properties differentiate them from the subsoil. The soil has been loosened by root growth, organic matter accumulation and decomposition have darkened its color, and some structure has developed. Stud- ies have shown that organic C content of the upper 10 cm of vegetated mine- soils may reach levels found in surrounding native soils within 30 to 50 yr (Hallberg et al., 1978; Schafer et al., 1980). However, organic C accumulates more slowly at depths below 10 cm where 400 yr or more may be required to reach levels comparable to native soils at observed rates of accumulation (Schafer et al., 1980). Physical and chemical weathering also may break down rock frag- ments very rapidly in near - surface environments (Ciolkosz et al., 1985), so that A horizons typically have lower rock fragment contents than subsurface hori- zons. Roberts et al. (1988a) noted a visible decrease in the rock fragment con- tent of A horizons over a 2 -yr period. In an Iowa loess spoil from a railroad cut (Hallberg et al., 1978), a 31 -cm thick A horizon developed in 100 yr. The color of the horizon was darker than the subsoil, but it was not dark enough to be mollic. Mining and reclamation methods determine the types of materials from which soils are reconstructed and affect the genesis of soil horizons. When prime farmland is mined, the A horizons and B horizons to a depth of 1 m must be stock- piled and returned to the surface of the reconstructed soil (SMCRA, 1977). This may not be a requirement on nonprime farmland. Bell et al. (1994) described 72 1- to 2 -yr -old reconstructed soil profiles on prime farmland in western Pennsyl- vania. They observed well- expressed Ap horizons on nearly all profiles. The prop- erties of these horizons were largely retained from the original replaced topsoil. In a 1980 study (unpublished data of the senior author) of minesoils devel- oping on anthracite coal mines in Pennsylvania, nine pedons were described and sampled (representative data in Table 23 -1). Three pedons were 3 yr old, three were 8 yr old, and three were 30 yr old. The 3- and 8 -yr -old sites had been regraded before revegetation, but the 30 -yr old site had not been regraded or revegetated, although it had some vegetation on it when the minesoils were described. The 8 -yr -old site had been planted to trees {red pine [Pinus resinosa Ait.], Austrian pine [P nigra Arnold], white pine [P strobus L.], and larch [Larix laricina (Du Roi) K. Koch }. The 3 -yr -old site had been seeded to grasses [tall fes- cue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.), timo- thy (Phleum pratense L.)], and some red pine and Norway spruce [Picea abies (L.) Karst.] had been planted. Lime and fertilizer had been applied to the 3 -yr -old site, but not to the 8 -yr -old site. The Peach Mountain coal seam had been mined at each site. This coal seam formed in the Llewellyn Formation during the Penn- sylvanian Period. Although all nine pedons developed in earth materials produced from the mining of the same coal seam, the mining and reclamation methods dif- fered. Therefore, it is difficult to relate age to soil development. Thickness of A horizons on the 30 -yr -old minesoils ranged from 5 to 15 cm and averaged 9 cm, MINESOIL GENESIS AND CLAS: Table 23 -1. Representative pedor minesoils in Pennsylvania. Depth Horizon cm Moist color 3 -vr -old site A 0-7 C l 7 -26 C2 26-110 8 -vr -old site A 0 -7 Cl 7 -28 30 -v__ r d s;te A 0-5 AC 5 -15 CI 15 -31 C 31 -71 C3 71 -114 IOYR 4/3 IOYR 5/8 IOYR 6/8 7.5 YR 6/8 10 YR 5/6 IOYR 4/3 7.5 YR 5/8 IOYR 3/3 1OYR 3/2 C2 28 -55 IOYR 4/4 7.5YR 5/6 N 2.5/0 C3 55 -100 1OYR 4/4 7.5YR 5/6 N 2.5/0 5YR 3/2 IOYR 5/3 IOYR 4/2 IOYR 6/6 1OYR 5/4 7.5YR 4/4 7.5YR 5/6 IOYR 4/1 g v v 'gr = gravelly, v = very, ch = channe cl = clay loam. ry e 1 = weak, f = fine, m = medium, gr = grai vfr = very friable, fr = friable, fi = firm. thickness of the 8 -yr -old A horizoi 6 cm, and thickness of the 3- yr -olc aged 8 cm. Erosion on steep slop( horizons from developing on the 3C the 3- and 8 -yr old pedons was 9% no clear differences in A horizon thi zons were described at the 30 -yr -old values of the 3 -yr old minesoil prof ever, higher pH's of the 3 -yr -old C2 of the parent materials rather than a Subsurface horizons have also Roberts et al. (1988b) described AC (1980) described shallow cambic -lil and Amos (1981) observed that can materials. In nontopsoiled minesoils