Natural Revegetation of an Unreclaimed Lignite Surface Mine in East-Central Texas

Abstract

Evaluating plants and soils on unreclaimed surface mines helps land managers un- derstand the effects of minesoil properties on plant growth and community development and may aid in the development of current reclamation plans. Eight unreclaimed surface mined sites in east-central Texas, ranging in age from 3 months to 50 years, were sampled to evaluate vegetation and minesoil changes over time and for comparison to an adjacent unmined area. Three- and 6-month-old unre- claimed areas had about 1% plant cover composed of pioneer grass and forb genera, including Di- chanthelium, Aster, Chenopodium, and Polygonum. Herbaceous plant cover increased from 12% on the 5-year-old site to a peak of 25% on the 20-year-old site. Dominant genera on 10- to 20-year-old sites were Andropogon, Bothriochloa, Cynodon, Dichanthelium, Paspalum, Aster, and Rumex. Woody species established as early as 5 years after mining (predominantly Baccharis salicina T. et G.), and canopy cover reached 14 and 35% on the 20- and 30-year-old sites, respectively. On the 50-year-old site, 17 woody species formed a multilayered vegetation structure with > 100% cover. Bulk density of minesoils in the surface 12 cm declined with time from 1.30 to <1.00 Mg/m3 as vegetation and litter increased. Undisturbed soils had an average pH of 5.9. Minesoil pH decreased from 6.9 on 3- and 6-month- old sites to 3.8 on 5- to 30-year-old sites (due to pyrite oxidation) and increased to 6.8 on the 50- year-old site. Several grass and forb species found on acidic minesoils in this study may be good candidates for low input revegetation programs for other postmining land uses.