Development of canopy cover and woody vegetation biomass on reclaimed and unreclaimed post-mining sites

•Difference in tree growth between spontaneous succession and reclaimed sites was studied.•Reclaimed sites however reached higher canopy cover and woody biomass in young sites.•In sites 20 years old and older no difference was found.

On an open-cast coal mining heap in the northwestern Czech Republic, development of the canopy cover of woody vegetation was studied using historical aerial photographs of unreclaimed sites overgrown by natural succession and of sites reclaimed by the planting of alder. A comparison of sites by general linear models revealed that canopy cover did not differ significantly between reclaimed sites and unreclaimed sites. Dominant species on unreclaimed sites (Salix caprea and Populus tremula) and reclaimed sites (Alnus glutinosa) sites were destructively sampled to generate site-specific allometric equations. Trees and shrubs were counted and measured on 5-, 19-, 15-, and 45-year-old reclaimed and unreclaimed sites. When sites were 5 years old, tree density was much higher on reclaimed sites (7575 trunks ha−1) than on unreclaimed sites (1215 trunks ha−1). On reclaimed sites, tree density gradually decreased with site age and was equivalent to that on unreclaimed sites when sites were 45 years old (1675 trunks ha−1). Woody biomass did not significantly differ between reclaimed and unreclaimed sites when measured across all ages but did significantly differ when measured at specific ages: thus, woody biomass was greater on reclaimed sites than on unreclaimed sites at age 5 years but was greater on unreclaimed sites than on reclaimed sites at age 25 years.