Forest harvest presents a potential threat to forest floor bryophyte communities primarily through alteration of the microclimate and disturbance of substrates on the forest floor. Management, including harvest, applied at the landscape scale creates patches of disturbance of differing severities at the spatial scale experienced by bryophytes. Presumably, bryophyte diversity in managed landscapes is best conserved by forest harvest techniques that minimize community change, thereby allowing disturbed communities to reassemble to approach predisturbance composition. We monitored bryophyte community reassembly by sampling quadrats established in a 54-ha management block of Acadian forest in New Brunswick, before and after harvest. Quadrats were either in unharvested areas, or experienced a range of disturbance severities from removal of some or all canopy, to forest floor disturbance with complete canopy removal. Bryophyte communities showed compositional change over 4 years, even in areas that were not harvested. Although species richness was maintained or recovered 4 years after harvest, changes in species composition were significant in all disturbance classes with greatest change related to forest floor disturbance. In particular, liverworts were lost in areas with forest floor disturbance. We suggest that the simplest method to reduce immediate species loss, and presumably promote conservation of bryophyte communities within managed forest landscapes, is to utilize techniques that reduce the area of forest floor and associated substrates that are physically disrupted.Key words: bryophyte, community change, disturbance, forest harvest, monitoring.

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The feather moss community in upland black spruce stands is dominated by Pleurozium schreberi, with small pure colonies and mixtures of ubiquitous and apparently persistent minor species. Previous studies indicated that this spatial pattern is not due to microsite conditions. This study tested the hypothesis that the minor species persist by dynamic occupation of small disturbance-type gaps. Colonization of experimental gaps (10 cm diameter, three substrate types) was tracked over 2 years to determine (i) how Pleurozium and the three minor species colonize gaps and (ii) how characteristics of the gaps affect colonization. All species colonized by encroachment of surrounding vegetative shoots. Availability of propagules, i.e., species composition of the surrounding bed, had the greatest impact, but regeneration of two species was affected by substrate: Ptilium growth was reduced on spruce needles, whereas that of Ptilidium was increased. Pleurozium schreberi displayed the most rapid growth in terms of shoot encroachment regardless of gap characteristics. By virtue of its abundant propagules and rapid growth, Pleurozium is most likely to colonize randomly located disturbance-type gaps, hence maintaining its dominance. Differentiation in regeneration characteristics does not account for the persistence of the minor species in the community. Keywords: Pleurozium schreberi, Ptilium crista-castrensis, Dicranum polysetum, Ptilidium ciliare, gap dynamics, community structure.

To address concern for loss of bryophyte biodiversity within managed forests, we compared community composition and environmental characteristics among three disturbance regimes: (i) naturally regenerated clear-cut forests, (ii) cutover spruce plantations (established on clear-cut forest land), and (iii) afforested field spruce plantations (established on agricultural fields) across a range of ages (19–102 years) in the Acadian Forest region of New Brunswick, Canada. Abundances of all forest floor bryophyte species, available substrates, microtopographical features, and tree canopy were measured as percent cover (1 m2) in 26 stands: 12 naturally regenerated clear-cut forests, eight cutover plantations, and six afforested field plantations. Multivariate analyses indicated that both bryophyte community composition and associated environment differed significantly across disturbance regimes, with no strong trends related to time since clearing (i.e., stand age). Spruce plantations were characterized by low substrate diversity and microtopographic and canopy homogeneity. Both plantation types had lower bryophyte species richness, evenness, and diversity (H') relative to naturally regenerated clear-cut forests; cutover plantations had the highest total bryophyte cover. The bryophyte community of plantations was composed of a subset of species found within naturally regenerated clear-cut forests: many liverworts and epixylic mosses were absent, with fewer pioneer species and more perennial stayers (equivalent to K-strategists) than expected.Key words: bryophyte, disturbance regime, substrate, canopy, microtopography, plantation.