The Effect of Topography on Long-Term Spontaneous Development of Soil and Woody Cover on Graded and Untreated Overburden

We studied the development of soil and soil fauna, as well as selected vegetation parameters important for litter input into soil, in two chronosequences of postmining sites after opencast lignite mining near the town of Most (Czechia). Both chronosequences did not have tree planting. On the first chronosequence, no leveling or any other measures had taken place after heaping, and the site kept the wavelike appearance created by the dumping process. The second chronosequence was formed by sites levelled by earthmoving machinery and in which shallow topsoil layers were spread. Both chronosequences were about 30 years old, and consisted of 8 and 11 sites for wavelike and levelled sites, respectively. In addition, samples were taken from a birch site outside of the heaps. Results showed differences in the development of tree and herb layers in both chronosequences. In the levelled sites, herb and tree cover increased after levelling, and woody cover developed much slower. In ungraded sites, woody cover developed faster, and the herb layer slower. Soil chemistry showed a similar pattern in both sites over time, characterized by a decrease in pH and sodium ion content. Soil macrofauna in levelled sites showed random oscillations, while it gradually increased with time in wavelike sites. The study suggested that site levelling alters long-term ecosystem development in postmining sites. Wavelike sites tend to develop towards pioneer forests, while leveled sites tend to be covered by grass and herb vegetation.