The Response of Spore Germination of Sphagnum Mosses to Single and Combined Fire-Related Cues

Abstract

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.

Keywords: fire disturbance; germination cue; persistence; spore germinability.

Figure 1

Effects of different heat temperatures on spore (a) viability (dyeing percentage) (b) germination percentage (GP) and in four Sphagnum species. Error bars represent SEM (n = 3). Lowercase letters (a, b and c) represent significant difference among species at the same heat temperature and uppercase letters (A, B, C and D) represent significant difference among heat temperatures in the same species (also in others). “α”, “β” and “γ” represent significant difference among the total germination percentage (21d) and viability after heat treatment.

Figure 2

Interactive effect between smoke–water and heat on spore germination percentage (GP) in four Sphagnum species ((a), Sphagnum angustifolium; (b), S. fuscum; (c), S. magellanicum; (d), S. squarrosum). Error bars represent SEM (n = 3). Lowercase letters (a, b and c) represent significant difference among smoke–water treatments at the same heat-shock temperature and uppercase letters (A, B, C and D) represent significant difference among heat temperatures at the same smoke–water treatment.

Figure 3

Interactive effect between smoke–water and heat on spore germination speed (GS) in four Sphagnum species. ((a), Sphagnum angustifolium; (b), S. fuscum; (c), S. magellanicum; (d), S. squarrosum). Error bars represent SEM (n = 3). Different lowercase letters represent significant differences (p < 0.05) between the treatments (smoke–water and heat treatments singly and combined).

Figure 4

Treatment effect index (TEI) of four Sphagnum species ((a), Sphagnum angustifolium; (b), S. fuscum; (c), S. magellanicum; (d), S. squarrosum) after single and combined treatment of heat temperature and smoke–water. Error bars represent SEM (n = 3). Different lowercase letters represent significant differences (p < 0.05) between heat treatments. Asterisks represent significant differences (p < 0.05) among smoke–water treatments at the same heat-shock temperature.