Snow chemistry and biological activity: a particular perspective on nutrient cycling

Abstract

The state-of-science on the effects of biological activity on snow cover is discussed. Except for some research that concerns the relationship of snow chemistry and snow algae the subject has received very little attention from snow chemists. This absence of studies relating biota directly to snow chemistry has led us to approach the subject by a theoretical treatise of nutrient dynamics in snow. The biogenic origins of nutrients in snowfall are described. The subsequent changes that could be expected in the concentrations of major nutrients (N, S, P, Ca, Mg, K) in forest snow cover have been estimated by comparing snow in open areas with that in litter-laden forest snowpacks and snow meltwaters. The influence that winter-active vertebrates and invertebrates could have on snow-nutrient fluxes have been calculated from data on the population densities of selected species and on the nutrient characteristics of excrement. Although the estimated biologically-induced fluxes are very variable due to the natural fluctuations of the snow-litter-animal ecosystems it is shown that the nutrient which is the most liable to biological activity in snow is nitrogen. N-depletion due to forest litter may attain 20--40 eq ha-1 during the spring melt period while algal demand can be 1--3 eq ha-1 day-1. Animal fluxes are associated mostly with mammalian herbivores and insects; deer, for example, can supply up to 20 eq N ha-1 day-1 to the snow cover and collembola may also excrete the same amount under conditions related to swarming on snow.