Seasonal changes in tree foliage and litterfall composition at reclaimed and unreclaimed post-mining sites

The afforestation of sites disturbed after coal mining has shown to be a favorite technique to restore all ecosystem functions. Leaf traits of trees used in restoration may substantially affect nutrient return decomposition rates in soil and thus, ecosystem development. The aim of the study was to compare seasonal changes between the individual tree species at two different sites focussing on seasonal changes of leaf biochemistry, elemental composition, and their role in nutrient return to the forest floor and nutrient cycling. Foliage and litterfall characteristics (specific leaf area (SLA), nutrients, phenolics, lignin, chlorophylls, and cellulose contents) were studied at two sites of the same age (25 years) with different tree species at post-mining sites at the Sokolov area around 50 degrees 14 ' 09 N and 12 degrees 39 ' 05 E (Czech Republic). The first two sites (unreclaimed) were left to spontaneous succession with a dominance of Betula pendula, Salix caprea, and Populus tremula. The second two sites (reclaimed) was land levelled and afforested by Alders (Alnus glutinosa, Alnus incana). The study showed that foliage quality and composition differed between individual tree species and between sites, especially in the contents of nitrogen (N), calcium (Ca), magnesium (Mg), potassium (K), and lignin concentration. Alder reclamation was most influenced by a symbiotic relationship with bacteria Frankia which support a high concentration of N in foliage and litterfall. However, the highest concentration of basic elements (Ca, Mg, K) was in foliage and litter of unreclaimed sites. A. incana had the highest content of lignin in foliage which increased steeply from August to September. Also, the content of lignin increased slightly in litterfall of unreclaimed sites during the vegetation season thought could have lead to slowing decomposition of litterfall and nutrient cycling in comparison to reclaimed sites.