火烧高温对泥炭藓孢子萌发力影响的模拟实验

Effects of high temperature during burning on Sphagnum spore germinability: A simulated experimental study

作为生态系统稳定性维持的一个重要因素,火对泥炭地优势植物泥炭藓(Sphagnum)孢子库的影响尚不清楚.以采自长白山区泥炭地的泥炭土和3种泥炭藓的成熟孢子为实验材料,室内模拟火烧,以此设置不同温度水平(20、40、60或100℃,持续0.5、1、2、4或10 min),对泥炭藓孢子进行热激处理,经萌发实验后,研究火烧高温对孢子萌发率的影响.结果显示,火烧期间各层土温随深度而递减,表层泥炭可达300℃的极端高温,而1 cm深温度仅为70℃,体现出泥炭土良好的热缓冲性;40℃的热激可使锈色泥炭藓(S.fuscum)与中位泥炭藓(S.magellanicum)孢子萌发率提高20%与50%;60℃的热激使尖叶泥炭藓(S.capillifolium)孢子的萌发率提高1倍;100℃热激对3种泥炭藓孢子萌发则有强烈的抑制作用.研究表明,泥炭藓孢子耐受高温的能力有限,但土壤中的孢子凭借泥炭的良好热缓冲性,可以躲避火烧高温造成的致命伤害,适度的热激甚至能提高其萌发力,对其在火后的建植及种群的长存可能有重要意义.

It is not clear how fire, an important factor maintaining ecosystem stability, affects spore banks of Sphagnum, the dominant plants in peatlands. In this study, mature spores of three Sphagnum species and peat soil collected from peatlands in the Changbai Mountains were used as experimental materials. We simulated a process of fire in laboratory and measured soil temperature at different depths. Four temperature levels (20, 40, 60 and 100 ℃) and five time levels (0.5, 1, 2, 4 and 10 min) were set to simulate a heat shock experiment to treat Sphagnum spores. The effects of temperature and time of heat shock on spore germination percentage were assessed with germination test. During the process of fire, temperature decreased with soil depth. Surface peat reached an extreme high temperature of 300 ℃, while it was only 70 ℃ at the layer 1 cm below the surface, reflecting the good thermal buffering property of peat soil. Compared to the treatment at 20 ℃, 40 ℃ heat shock increased 20% of spore germination percentage of S. fuscum and 50% of S. magellanicum, while 60 ℃ heat shock could double the spore germination percentage of S. capillifolium. In contrast, 100 ℃ treatment strongly decreased spore germinability. Our results indicate that the efficient thermal insulation of peat soil may keep Sphagnum spores away from lethal high temperature and that moderate heat shock may facilitate spore germination of Sphagnum. These may be of great significance for the establishment of Sphagnum spores in peat and population persistence in response to fire disturbance.