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Advantages of mixed tree stands in restoration of upper soil layers on postmining sites: A five‐year leaf litter decomposition experiment

Horodecki, Paweł, Nowiński, Mirosław, Jagodziński, Andrzej M.
Land degradation & development 2019 v.30 no.1 pp. 3-13
Acer pseudoplatanus, Alnus glutinosa, Betula pendula, Fagus sylvatica, Fraxinus excelsior, Pinus sylvestris, Populus canadensis, Populus nigra, Populus tremula, Prunus serotina, Quercus robur, Quercus rubra, Robinia pseudoacacia, Ulmus, calcium, lignite, magnesium, mine spoil, mixed stands, plant litter, planting, pure stands, soil formation, soil horizons, species diversity, trees, Poland
No in‐depth studies covering litter decomposition were previously conducted on afforested postmining sites despite the importance of litter decomposition on soil formation, especially in degraded areas. We aimed to compare leaf litter decomposition rates of 14 tree species growing in mixed stands on a postmining spoil heap, and to compare their decay rates with those obtained in pure stands of tree species that are very often planted in postmining areas. The study was conducted on the Bełchatów Lignite Mine spoil heap, central Poland. We studied litter decomposition rates over 5 years using the litterbag method. Leaf litter decomposition rates (k constants; yr⁻¹) after 5 years of the experiment were arranged from highest to lowest as follows: Prunus serotina (1.04), Alnus glutinosa (0.86), Fraxinus excelsior (0.81), Ulmus laevis (0.73), Acer pseudoplatanus (0.68), Populus tremula (0.63), Populus × canadensis (0.59), Betula pendula (0.54), Populus nigra ‘Italica’ (0.38), Quercus rubra (0.36), Pinus sylvestris (0.34), Robinia pseudoacacia (0.34), Fagus sylvatica (0.25), and Quercus robur (0.22). Decomposition rates increased with Mg, Ca, and summed Mg + Ca + P + K contents in freshly fallen leaves (%). All species‐specific decomposition rates were higher in mixed than in Scots pine stands. Half of them were also higher than in pure stands of other tree species. Our results indicate that tree species composition could significantly affect the physiochemical properties of upper soil horizons on reclaimed areas. Based on these findings, we recommend planting high share of not only A. pseudoplatanus, A. glutinosa, and U. laevis but also F. sylvatica and Q. robur in stands on postmining spoil heaps, because mixed stands can accelerate soil development more than pure stands.