Nutrient leaching from dormant trees at an elevated site

Abstract

Observations are presented on ion concentration in winter deposits to coniferous and deciduous trees at an elevated site (860 m). Such sites, with persistent snow and ice cover and considerable deposition of atmospheric pollutants, are common in Eastern Canada and the North-Eastern U.S. Spot samples at a given sampling date and samples of total deposits accumulated over extended periods of time were taken during the winters of 1986–87 and 1987–88. Samples were analyzed for pH and the major anion and cations. Results of spot samples were similar between different sampling times (and years) for deposits on balsam fir but variable for those on branches and twigs of deciduous trees (birch, choke cherry). The chemistries of snow on the ground and snow on trees not in contact with foliage or branches were found not to be significantly different statistically (p<0.05). However, significant differences exist between concentrations of nutrient ions in snow and ice with and without contact with biological elements of coniferous and deciduous trees. This indicates occurrence of nutrient leaching during winter conditions, leading to possibly non-negligent nutrient stress for K− and Mg−. Based on spot and cumulative samples for balsam fir, and correcting for possible contributions from dry deposition, the contribution from leaching in winter deposits on balsam fir foliage has been estimated at 26, 14 and 9 μeq L⁻¹, for K⁺, Ca⁺⁺ and Mg⁺⁺, respectively. With approximate estimates of stand characteristics and precipitation loading at the sampling sites, these figures represent 90/c, 1% and 8%, respectively, of the estimated annual growth component of the stand for K⁺, Ca⁺⁺ and Mg⁺⁺ This indicates the possibility of non-negligible nutrient stress for K⁺ and Mg⁺ during winter conditions at the given site.