*2.3. Laboratory Analyses*

In total, 70 soil and 52 vegetation (25 *A*. *flexuosa*, 27 *V*. *myrtillus*) samples were analyzed by the Wageningen University Testing Laboratory of the Resource Ecology Group.

In soil, the concentrations of total nitrogen (N), total phosphorus (P) and calcium (Ca) were determined after digestion with H2SO4 <sup>−</sup>Se-salicylacid-H2O2 [34,35]. Concentrations of inorganic nitrogen (nitrate NO3 <sup>−</sup>, ammonium NH4 <sup>+</sup>), inorganic phosphorus (phosphate PO4 −), potassium (K), magnesium (Mg) and sodium (Na) in soil were determined after extraction with 0.01 M CaCl2 by using the method described in [36].

In plant leaves, the concentrations of total N, total P, Ca, K, Mg and Na were determined by digestion with H2SO4 <sup>−</sup>Se-salicylacid-H2O2. The C/N ratio in both soil and vegetation was determined using a C/N analyzer (Fisons EA 1108, CHN-0, Woodstock III, Interscience B.V., Breda, Brabant, The Netherlands). Concentrations of total N and total P in soil and vegetation, and inorganic nitrogen (nitrate NO3 <sup>−</sup>, ammonium NH4 <sup>+</sup>) and inorganic phosphorus (phosphate PO4 −) in soil were measured with an auto-analyzer (Skalar San Plus, colorimetric system, Skalar Analytical B.V., Breda, Noord-Brabant, The Netherlands). K, Ca, Mg and Na were measured with an atomic absorption spectrometer (Varian, SpectrAA-600, Varian B.V. Benelux, Middelburg, Zeeland, The Netherlands).
