Decomposition rates of bryophytes in managed boreal forests: influence of bryophyte species and forest harvesting

Abstract

The slow decomposition rate of boreal forest floor bryophytes contributes both to maintaining high soil C reserves as well as affecting conditions for tree growth by maintaining excessively high soil water content, cooling the soil and slowing nutrient cycles. In this study, mass loss of three bryophyte species (Pleurozium schreberi, Sphagnum capillifolium, S. fuscum) was measured in unharvested, partial cut and low-retention cut forest blocks. Mesh decomposition bags containing the three species and wood sticks were placed at two depths in colonies of either P. schreberi or S. capillifolium (environment) in the three harvest treatments and retrieved after two growing seasons. Mass loss was primarily related to substrate type (P. schreberi > S. capillifolium > wood sticks > S. fuscum) and secondarily to depth. Harvest treatment and environment (P. schreberi or S. capillifolium) only weakly affected sphagna mass loss. The weak effect of harvest treatment suggests that conditions created by low retention cuts do not to stimulate decomposition in this system and are not important enough to stimulate carbon loss, or to counteract paludification. On the other hand, the strong effect of bryophyte type indicates that conditions affecting bryophyte colonization and succession are of great importance in driving carbon and nutrient cycles.

The Impact of Moss Species and Biomass on the Growth of Pinus sylvestris Tree Seedlings at Different Precipitation Frequencies

“…These reference samples were also used to establish the relationship between the fresh weight (saturated conditions) and dry weight of individual moss cushions (Table S1). The mosses were therefore cleaned from litter and any other moss species present, saturated by submerging in water for at least 30 minutes, spun with 20 pulses for approximately one minute to release external water according to Fenton et al [59], weighed (to obtain the fresh weight) and then oven dried (70 °C, 48 hours) and weighed again to get the oven-dry weight. Table S1.…”

Managing Understory Vegetation for Maintaining Productivity in Black Spruce Forests: A Synthesis within a Multi-Scale Research Model

“…Similarly, stands with a closed canopy tend to be dominated by feather mosses [66], which have a lower photosynthetic compensation point than Sphagnum species [67]. Our studies showed a positive feedback loop in the paludification process: as stands open up through natural self-thinning, Sphagnum species dominate and replace feather mosses [66], stimulating the accumulation of the organic layer via their slow decomposition rate [59,60] and their faster growth rate [68]. This thick organic layer results in an elevated water table [66], which creates a wet, cold, nutrient poor rooting environment for trees.…”

“…Studies have shown that not only do feather mosses (such as P. schreberi) harbour N fixing cyanobacteria [57], but also that black spruce is able to absorb this organic N [58]. Furthermore, Sphagnum species have particularly slow decomposition rates [59,60], which are not fully explained by their high C:N, but are probably a function of various secondary metabolites that limit microbial breakdown of their cell walls [61]. This fundamental knowledge raised questions that needed to be addressed at a coarser scale of analysis: what are the drivers of paludification at the site level, and what are the best techniques to manage paludified stands?…”

From Litter to Humus in a Norwegian Spruce Forest: Long-Term Studies on the Decomposition of Needles and Cones

“…Nordic coniferous forests often have a several cm thick moss cover on the ground. Moss plants produce considerable amounts of litter and the moss litter of boreal forest floors decomposes slowly [37,38]. At the present study site, moss litter was easily defined in layers which were at least six years old [17].…”