Experimental evidence for a persistent spore bank in Sphagnum

Area of Science:

• Ecology
• Bryology
• Plant Science

Background:

• Sphagnum mosses are crucial peatland dominants.
• Understanding Sphagnum spore longevity is key to peatland ecology and restoration.
• Previous research on bryophyte spore and wetland seed longevity provides context.

Purpose of the Study:

• To investigate the viability and longevity of Sphagnum spore capsules buried at various depths.
• To determine factors influencing Sphagnum spore survival, including time, depth, moisture, and oxygen.
• To assess the potential for Sphagnum spores to form a persistent, long-term spore bank.

Main Methods:

• Spore capsules of four Sphagnum species were buried in peat at different depths.
• Spore viability was assessed after 0, 1, 2, and 3 years.
• Factors like light spore color, spore size, capsule size, moisture, and oxygen levels were considered.

Main Results:

• Viability generally decreased over time, but viable spores persisted for at least 3 years.
• Lighter-colored spores (S. balticum, S. tenellum) showed better viability than darker ones (S. fuscum, S. lindbergii).
• Optimal survival occurred under wet, aerobic conditions; high survival also noted under humid or periodically desiccated conditions. Anaerobic conditions led to rapid spore death.
• No correlation between spore size and longevity, but smaller spores from smaller capsules showed higher viability.
• Indicated conditional dormancy influenced by weather.
• Estimated spore bank half-life between 1-20 years, with potential for decades to centuries.

Conclusions:

• Sphagnum spores can form a long-term persistent spore bank, crucial for species' wide distribution.
• Environmental conditions, particularly moisture and oxygen availability, significantly impact spore longevity.
• Spore characteristics like color and potentially size within species may influence survival and dispersal potential.
• Findings challenge some previous assumptions about bryophyte spore and wetland seed longevity.