Seasonal Dynamics of Foliage Macronutrient Concentrations in Black Alder (Alnus glutinosa (L.) Gaertn.) Growing on Nutrient-Poor Post-Mining and Fertile Natural Soils

Black alder (Alnus glutinosa) is widely used to reclaim nutrient-poor post-mining soils, yet how adverse conditions affect seasonal foliar macronutrient dynamics and resorption remains unclear. We compared seasonal changes in leaf C, N, P, K, S, Ca, and Mg concentrations in A. glutinosa on an extremely nutrient-poor sandy Technosol versus a fertile Gleysol during the growing season. Seasonal macronutrient patterns were similar at both sites: N and S concentrations remained stable, P and K declined toward autumn, and Ca and Mg increased. Trees growing on Technosol exhibited lower late-season K concentrations, indicating K limitation under poor, drought-prone conditions, whereas foliar N and P differed minimally between sites. Resorption was element-specific rather than site-specific: P exhibited the highest resorption efficiency, while K resorption was higher on the Technosol. Neither Ca nor Mg was significantly resorbed. These findings confirm black alder’s suitability for post-mining reclamation due to robust N and P acquisition, while highlighting potassium as the primary limiting nutrient on sandy mine soils.