Plants in flammable ecosystems have different response strategies to fire, such as increasing germination after exposure to smoke and break of dormancy through heat shock. Peatlands are ecosystems that are more likely to be disturbed by fire with increasing temperatures, but it is not clear how fire affects spore germination of Sphagnum, the dominant plants in peatlands. Here, we hypothesize that Sphagnum spores respond positively to single and combined treatments of moderate heat and smoke (by increased germinability), while spore germinability decreases in response to high temperature. We exposed the Sphagnum spores of four selected species (S. angustifolium, S. fuscum, S. magellanicum and S. squarrosum) collected from peatlands in the Changbai Mountains to heat (40, 60 and 100 °C), on its own and combined with smoke-water treatments. Our results showed that a heat of 100 °C inhibited the spore germination or even killed spores of all species, while spore germination of three (Sphagnumangustifolium, S. fuscum and S. squarrosum) of the four species was promoted by 40 and 60 °C heat compared to the control (20 °C). Hollow species (S. angustifolium and S. squarrosum) showed a stronger positive responsive to heat than hummock species (S. fuscum and S. magellanicum). Sphagnumfuscum spores responded positively to the combined heat and smoke treatment while the other species did not. For the first time, we demonstrate the positive effects of heat on its own and in combination with smoke on spore germination in wetland mosses, which may be important for the establishment and persistence of peatmoss populations after fire.

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

Dry/wet cycling driven by water level fluctuation in wetlands may strongly influence the destiny of seeds. However, how dry/wet cycling affects spore survival and germinability in peatland bryophytes is poorly understood.• Six peatland bryophytes, three hummock-and three hollow-dwelling Sphagnum species, were chosen as study species. We tested the effects of dry (60% air RH)/wet (waterlogging) cycle frequency (once per 12, 8 or 4 days for low, medium or high, respectively) and ratio (3:1, 1:1 or 1:3 dry:wet time per cycle) on spore germinability, viability, dormancy percentage and protonema development.• Dry/wet cycling significantly reduced spore germination percentage and viability and slowed protonema development in all Sphagnum species, being more pronounced with higher dry/wet cycling frequencies. The hummock species S. capillifolium and S. fuscum had higher spore germination percentage after the continuous dry treatment, while the hollow species S. angustifolium, S. squarrosum and S. subsecundum showed the opposite response, compared to the continuously wet treatment. Except for S. squarrosum, spore viability was higher after the dry than after the wet treatment. Spore viability and dormancy percentage were higher after a dry/wet ratio of 1:3 than after ratios of 3:1 and 1:1.• Our study shows that both germinability and viability of bryophyte spores are reduced by dry/wet cycling (especially when frequent) in peatlands. This emphasizes the need to ensure constant water levels and low frequencies of water level fluctuation, which are relevant in connection with wetland restoration, to promote Sphagnum spore survival and establishment in peatlands after disturbances.