Roles of Bryophytes in Forest Sustainability—Positive or Negative?

Bryophytes were traditionally ignored in most studies of forest ecosystem processes, or they were included with litter or soil. In the last few decades we have begun to understand their many roles that permit them to be ecosystem engineers. This review serves to pull together many scattered sources into a single source on the many contributions bryophytes can perform as ecosystem engineers and to support what several authors have already stressed: that bryophytes should not be treated as a single functional group. It puts bryophytes in perspective in terms of richness and biomass, then explores their roles as ecosystem engineers; that is, their roles in altering diversity, nutrient cycling, carbon sequestering, water retention, erosion depression, temperature modification, fire protection, fire and logging recovery, interactions with mycorrhizal fungi, effects on seed germination, and seedling survival. Interactions with other species are mentioned, but those regarding animals are largely omitted in favor of more detailed description of their relationships with trees throughout the world. Bryophytes provide both positive and negative interactions with forest trees, depending on the tree species, the ecosystem, and the bryophyte species. It is clear that different bryophytes have many different functional roles in sustaining the forest and making it suitable for germination, seedling success, and maintaining the mature forest. This review indicates those important roles and how they apply differently according to both tree and bryophyte species, and that different management practices are needed, depending on both bryophyte species and tree species, to sustain different forest types.