Nutrient Distribution in Silver Birch (Betula Pendula Roth) Biomass Growing on Post-Arable Soils

Abstract

The afforestation of former farmland is a common practice on poor-quality soils when traditional production is no longer profitable. To at least maintain, and preferably improve, the health and quality of the soil––key assumptions of afforestation––it is crucial to understand the effects of various tree species on the soil environment. Tracking nutrients, including their contents, forms, bioavailability, uptake, bioaccumulation in the biomass, and return to the soil via litterfall, is important in this regard. Although silver birch––a species with a wide tolerance for various site conditions––is often implemented in afforestation, knowledge concerning its ecology is still insufficient, including the nutrient aspects. Hence, we undertook a broad study to determine the bioaccumulation of major nutrients in the biomass of silver birch trees growing on post-arable soils, representing various trophic states and degrees of deformation, under temperate climatic conditions, focusing on nitrogen (N), phosphorus (P), potassium (K), iron, calcium (Ca), magnesium (Mg), sulfur (S), manganese (Mn), copper (Cu), and zinc (Zn). The study covered four stands representing varied soil textural characteristics (loamy and sandy) and ages (10 and 35 years). Samples of soil (from depths of 0–10, 10–20, 20–40, and 40–80 cm) and biomass (fine roots, coarse roots, stemwood, bark, coarse branches, fine branches, and leaves) were collected, with 10 replicates per stand, and analyzed using standard procedures. The soils were acidic and moderately abundant in total organic carbon and N, but generally poor in the remaining elements. The elemental contents strongly varied among the birch organs, commonly reaching their highest values in the leaves, followed by the roots (N, P, K, Mg, S), bark (Mn, Cu), and branches (Ca). Iron occurred in its highest amounts in the fine roots, Zn in the bark. Among the macronutrients, the highest bioaccumulation intensity was recorded for N, followed by S, P, and Ca, while the highest intensity among the micronutrients was for Zn. Statistically significant differences were noted in several cases between the stands, in terms of individual biomass fractions and their elemental contents and bioaccumulation factors. Our results highlight the influence of soil properties and the post-arable nature of the stand on the nutrient accumulation in silver birch biomass. We found that silver birch growing on former arable soils show an increased accumulation of some nutrients, particularly P and S. Moreover, the strong accumulation of Zn and Mn by this species was confirmed.

Keywords: Silver birch, biogeochemical cycling, nutrients, bioaccumulation, marginal soils