Buxbaumia is an odd-looking moss genus that draws attention beyond bryologists. Especially Buxbaumia viridis is an important species as it is listed under Annex II of the EU Habitats Directive, B. viridis is recognized as a species requiring strict protection and the designation of Special Areas of Conservation across Europe (European Commission, 2020). But there’s more to this moss than meets the eye.
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| Buxbaumia viridis sporophyte |
Ecology and Habitat
Traditionally, Buxbaumia viridis has been viewed as a forest specialist, confined to pristine, old-growth coniferous forests where decaying wood and constant humidity provide a stable microhabitat. The European Commission notes that the species is especially sensitive to changes in forest structure and the availability of deadwood (European Commission, 2020).
Surprisingly, recent studies found B. viridis in disturbed and managed environments as well (Deme et al., 2020), suggesting a broader ecological niche than once believed.
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| Spruce monoculture supports Buxbaumia viridis in northern bavaria |
Deadwood Dependency
Buxbaumia viridis is epixylic—it grows on dead wood. Whether it’s decaying spruce logs in Poland (Cykowska & Vončina, 2011) or decomposed trunks in the old-growth forests of Montenegro (Dragićević et al., 2012), B. viridis depends on well-decayed wood, particularly in intermediate to advanced stages of decomposition (Kropik et al., 2020).
Moisture Sensitivity
Humidity is another crucial factor. The species grows in constantly humid forests (Dragićević et al., 2012) and needs stable moisture levels to support both protonemal and sporophyte stages (Holá et al., 2014).
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| typical Buxbaumia viridis habitat |
Life Cycle: Two Lives in One
What makes Buxbaumia viridis even more interesting is its dual life strategy. Its protonemal stage is independent and can can establish on less decomposed wood and occurs in a wider range of forest types—including broad-leaved forests at lower elevations (Guillet et al., 2021). This stage is more widespread than the sporophyte and has a greater ecological flexibility. The gametophyte is extremely reduced and mostly invisible.
The sporophyte, by contrast, is more demanding. It typically develops in coniferous forests at higher elevations and is strongly influenced by deadwood decay stage and light availability. Sporophytes are most frequent on higly decayed wood and under more open canopies, while protonemal colonies prefer shaded microsites (Kropik et al., 2020; Guillet et al., 2021).
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| Sporophytic stage with extremely reduced gametophyte |
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| Protonemal stage |
Indicator Species—With a Twist
For years, Buxbaumia viridis has served as a bioindicator for old-growth coniferous forest. However, this role is being re-evaluated. Studies from Hungary and Italy show that it can persist in managed forests as well, if the deadwood and humidity requirements are met (Deme et al., 2020; Puntillo & Puntillo, 2024). From field observations, I can also state that it occurs in planted spruce monocultures and especially the gemmae are very common in any moist spruce forest in bavaria.
The Role of Climate and Forest Management
Climate is probably a major driver in B. viridis distribution. Dry periods longer than 9.6 consecutive days significantly reduce its chances of survival (Kropik et al., 2020). This makes of course vulnerable to climate change and improper forest management. While managed forests can host the species, practices that reduce canopy cover, remove deadwood, or increase desiccation risk can still threaten its persistence.
Conclusion
Buxbaumia viridis is a small moss with a complex ecological story. Once considered a relic of old-growth forests, it’s now seen as a species with surprising adaptability—able to colonize managed forests when conditions are right.
References
Cykowska, B., & Vončina, G. (2011). Recent occurrence of moss Buxbaumia viridis (Bryophyta, Buxbaumiaceae) in the Kłodzko region (Central and Eastern Sudetes, SW Poland). Bryologist.
Deme, J., Erzberger, P., Kovács, D., Tóth, I., & Csiky, J. (2020). Buxbaumia viridis (Moug. ex Lam. & DC.) Brid. ex Moug. & Nestl. in Hungary predominantly terricolous and found in managed forests. Cryptogamie. Bryologie.
Deme, J., & Csiky, J. (2021). Development and survival of Buxbaumia viridis sporophytes in Hungary. Journal of Bryology.
Dragićević, S., Papp, B., & Erzberger, P. (2012). Distribution of Buxbaumia viridis in Montenegro. Bryologist.
European Commission. (2020). Habitat types and species under the EU Habitats Directive. https://ec.europa.eu/environment/nature/natura2000/index_en.htm
Guillet, A., Hugonnot, V., & Pépin, F. (2021). The habitat of the neglected independent protonemal stage of Buxbaumia viridis. Plants, 10(4), 718.
Holá, E., Vrba, J., Linhartová, R., Novozámská, E., Zmrhalová, M., et al. (2014). Thirteen years on the hunt for Buxbaumia viridis in the Czech Republic: Still on the tip of the iceberg? Bryologist, 117(2), 159–168.
Kropik, M., Zechmeister, H., & Moser, D. (2020). Climate variables outstrip deadwood amount: Desiccation as the main trigger for Buxbaumia viridis occurrence. Plants, 9(6), 720.
Puntillo, D., & Puntillo, M. (2024). Monitoring of Buxbaumia viridis in Calabria (southern Italy) with some historical and ecological notes. Borziana.
Wiklund, K. (2002). Substratum preference, spore output and temporal variation in sporophyte production of the epixylic moss Buxbaumia viridis. Journal of Bryology, 24(2), 97–103.