Smoke responsiveness of peatland bryophyte spores

Northern peatlands are globally important carbon stores, but with increasing fire frequency, the re-establishment of bryophytes (notably Sphagnum) becomes crucial for their carbon sequestration. Smoke-responsive germination is a common trait in seeds in fire-prone ecosystems but has not been demonstrated in bryophyte spores. To investigate the potential role of smoke in post-fire peatland recovery, we tested the germination of spores of fifteen bryophyte species after treatment with smoke-water. Comparison of smoke responsiveness between spores of different laboratory storage times and burial depths/age (3-200 yrs old) were subsequently tested. Smoke increased germination percentage for 10 of the 15 study species, and increased germination speed for four of these. Smoke responsiveness increased along the fire frequency gradient from open expanse to forest margin, consistent with the theory that this selects for the maintenance of fire-adapted traits. Smoke enhanced germinability of 1-yr but not 4-yr laboratory-stored spores. Smoke, however, considerably increased germinability of spores naturally buried in peat for decades and up to c. 200 yrs. The effect of fire may be overlooked in non-fire-prone ecosystems, e.g. those in which wetland bryophytes dominate. Hence, an expected increase in fire frequency may lead to shifts in species dominance, for which our study provides one mechanism, which may affect long-term carbon sequestration in peatlands.