Paper Birch ( Betula papyrifera ) Nutrient Resorption Rates on Nutrient-Poor Metal-Contaminated Soils and Mine Tailings

Acidic, metalliferous mine tailings are hostile environments for vegetation growth. Despite this, Betula papyrifera (paper birch) has emerged as a primary colonizer in metal contaminated areas. This study assessed foliar nutrient resorption efficiency and proficiency in B. papyrifera growing on two Ni-Cu (nickel-copper) tailings sites and two smelter-impacted sites near Sudbury, Ontario, in Canada. Soils at the smelter-impacted sites were more acidic, with significantly higher OM (organic matter) and P (phosphorus), whereas soil at the tailings sites had much higher concentrations of many metals. The primary limiting nutrients in the tailings were P and K (potassium), which were below reported foliar critical thresholds for paper birch, whereas foliar nitrogen (N) concentrations indicated sufficiency. Despite much lower pre-senescence foliar P and K concentrations, trees growing on tailings did not resorb nutrients more effectively than those at smelter-impacted sites. Wide within-site variation in foliar nutrient resorption efficiency and proficiency may indicate that there are physiological constraints to nutrient resorption in contaminated sites, preventing trees from fully resorbing foliar P and K. The similarities in P resorption proficiency despite large differences in pre-senescence chemistry indicate that there may be critical physiological limits below which paper birch are incapable of resorbing nutrients.