Bryophytes and Revegetation of Coal Spoils in Southern Iowa

Abstract

Strip mining of coal in southern Iowa has left many scattered areas of coal spoils which provide a type of habitat unique to the region. The occurrence and distribution of 29 mosses and 2 liverworts on spoils of varying age was determined and related to processes of spoil revegetation. A higher percent cover and a greater species diversity of bryophytes was observed on the older spoils which appeared to be correlated with increased vascular plant cover. Dicranella heteromalla (Hedw.) Schimp. and Ceratodon purpureus (Hedw.) Brid. were found to be common throughout the spoils, whereas all other species were limited to more protected sites, especially on well vegetated, north-facing slopes. Mosses did not appear to colonize areas exposed to severe erosion, but were limited to areas with some protection provided, especially by vascular plants. Several disjunct or highly localized moss populations were found, including one new state record and thirteen new county records. During the past 50 years, strip mining of coal in southern Iowa has resulted in destruction of about 4450 ha (11,000 acres) of land. In the strip mining process the soil and rock strata overlying the coal, the overburden, are scooped off to expose the coal seam leaving a series of ridges and valleys, frequently with pools of water in the very low valleys. The resultant topography and soils are generally referred to as spoil banks or coal spoils. The typical undisturbed overburden in southern Iowa is composed of (from top to bottom) Wisconsin loess, Kansas glacial till, buff-colored shale and sandstone, gray shale and dark gray shale, all lying above coal-bearing rocks of Pennsylvanian age (Einspahr et al., 1955). Composition of the spoils varies, depending on how the overburden was mixed and deposited in a given place, but generally the order of the strata is essentially reversed, leaving the shales and sandstones exposed on the surface. Spoils usually are composed of a mixture of rock fragments ranging in size from massive chunks of shale and sandstone to sand, silt and clay-sized particles (Cummins et al., 1966). Many spoils are acid due to oxidation of sulfur-bearing minerals, primarily pyrite, markasite and poly-sulfides. These minerals occur in the shales overlying the coal, and acidity develops when this part of the overburden is left on the surface. The effect of this acidity on availability and solubility of chemical elements is recognized as a major problem in spoil revegetation. Especially important are iron, aluminum and manganese which are highly soluble at low pH and frequently reach toxic levels on coal 1Work sponsored by the Iowa Coal Project and conducted in the Energy and Mineral Resources Research Institute at Iowa State University. We are grateful to Dr. Paul L. Redfearn, Jr. for verification of species identifications and to Dr. Howard Crum for identification of Sphagnum. We also thank the owners of the strip-mine study areas for access to their land. 2 Dept. of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50011. This content downloaded from 157.55.39.153 on Mon, 19 Sep 2016 04:57:25 UTC All use subject to http://about.jstor.org/terms 1977] CARVEY ET AL.: BRYOPHYTES AND REVEGETATION OF COAL SPOILS 631