Chemical quality of aboveground litter inputs for jack pine and black spruce stands along the Canadian Boreal Forest Transect Case Study

Abstract

In the Canadian boreal forest, jack pine stands generally have a thin forest floor and occupy sites with coarsetextured soils and good drainage. Black spruce occurs more often on poorly drained sites and develops a thick mossdominated forest floor, but the common attribution of this development to poor quality of black spruce foliar litter has not been tested. We determined needle, twig, cone, and bark litter inputs during 10 y for black spruce and jack pine along the Boreal Forest Transect Case Study in northern Saskatchewan and Manitoba. Analysis of C, N, total phenolics, condensed tannins, and solid-state 13C NMR spectra from years 1–3 showed only small differences between species, notably higher tannins in black spruce cones. There was similarly little difference between area-based inputs, including classes of C structures determined by NMR. Condensed tannin input for black spruce was approximately twice that for jack pine, but both were in the very low range of reported values. Similar analyses showed that black spruce forest floor was less decomposed than that of jack pine, and for both species, aromatic litter C inputs appear to be poorly conserved, with a large influence of mosses and lichen. It is unlikely, however, that these large differences are mainly due to the small differences in aboveground litter inputs.