Ecological studies in the boreal spruce–fir forests of the North American taiga. II. Analysis of the bryophyte flora

Abstract

The bryoflora of 34 white spruce – fir and 26 black spruce stands in the boreal forest subzone consisted of 100 mosses and 33 liverworts. Short turfs, smooth mats, threaded mats, and tall erect turfs were the most species-rich growth-forms; wefts were cover dominants. White spruce – fir stands had more species but lower cover than black spruce. The liverwort:moss species ratio in white spruce – fir increased with precipitation. Based on bryoflora and geography, stands were classified as follows: white spruce – fir, Hylocomium splendens – Pleurozium schreberi order (= three associations of western Ceratodon purpureus – Pylaisiella polyantha alliance and two associations of eastern Rhynchostegium serrulatum – Tetraphis pellucida alliance); black spruce, Pleurozium schreberi – Hylocomium splendens order (= three associations of western Drepanocladus uncinatus – Brachythecium salebrosum alliance and two associations of eastern Sphagnum – Hypnum pallescens alliance). Of the 32 most important species, 16 'preferred' wood, 7 needle litter, 6 mineral soil, and 3 bark. The ground cover hierarchy in white spruce – fir was weft mosses > detritus [Formula: see text] needles > wood > other bryophytes > lichens > bark > soil; in black spruce, wood and other bryophytes were reversed. Higher species richness of white spruce – fir stands was ascribed to higher productivity and greater age, which gives a greater diversity and quantity of woody substrates for microsuccessional species. Shortage of suitable substrate and competition from weft mosses may explain the consistently low abundance of most other bryophytes in the two community types.