by Piter Kehoma Boll
Among the many different ecosystems found on Earth, bogs are particularly interesting. These peculiar wetlands are basically a large amount of water-soaked plant matter, either dead or alive. Usually very acidic, bogs have very low decomposition rates, so plant matter tends to accumulate more and more, sometimes reaching several meters in depth.
The main organisms responsible for the formation of bogs are mosses of the genus Sphagnum, commonly known as bogmosses or peatmosses (peat being the plant material that forms the bogs). Found all around the world, bogmosses have the ability to absorb huge amounts of water, just like a sponge, and in dry conditions they can release this water into the surrounding areas, helping them stay humid.
One bogmoss species, the red bogmoss, Sphagnum capillifolium, is found in the northern half of North America and Europe, being an important and genetically diverse species. In fact, it is likely that the red bogmoss is actually a complex of many very similar species. Its scientific name, capillifolium, meaning “hair-leaf”, refers to the peculiar shape of the plant, which grows in straight and densely packed branches that bent outwards at the top, resembling tresses.
Although most bogmoss species are green like any regular plant, the red bogmoss and closely related species can have a reddish color. However, this color is not caused by pigments in their plastids but by a pigment, sphagnorubin, found in their cell walls. The presence or not of sphagnorubin seems to be determined by certain combinations of temperature, light and hormones. The exact function of sphagnorubin is unknown, but there have been suggestions that it may help protect the plant from herbivory. It i also possible that this reddish color works as a sunscreen, protecting the plant’s chloroplasts from intense radiation since sphagnorubin absorbs UV and blue light.
Bogmosses in general are not attractive to herbivores because they contain high amounts of phenolic compounds, such as tannins, which gave them an adstringent and bitter taste. These phenolic compounds are also the main reason why peat takes such a long time to decompose. As a result, bogs function as huge carbon reservoirs, and about 10 to 15% of all carbon stock on the planet is in the form of Sphagnum. In fact, the amount of carbon fixed by all other photosynthetic lifeforms on Earth every year is lower than the amount held in bogs.
Sphagnum is, thus, an essential genus to keep the levels of carbon dioxide in the atmosphere low and the red bogmoss is even more important because it seems to be a very tolerant species that can survive in both shaded and sunny environments, as well as conditions with low and high levels of nitrogen and may, therefore, resist human interference better than other bogmosses.
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References:
Bonnett SAF, Ostle N, Freeman C (2009) Short-term effect of deep shade and enhanced nitrogen supply on Sphagnum capillifolium morphophysiology. Plant Ecology 207: 347–358. https://doi.org/10.1007/s11258-009-9678-0
Gerdol R, Bonora A, Marchesini R, Gualandri R, Pancaldi S (1998) Growth Response of Sphagnum capillifolium to Nighttime Temperature and Nutrient Level: Mechanisms and Implications for Global Change. Arctic and Alpine Research 30(4): 288–395. https://doi.org/10.1080/00040851.1998.12002914
Verhoeven JTA, Liefveld WM (1997) The ecological significance of organochemical compounds in Sphagnum. Acta botanica neerlandica 46(2): 117–130. http://natuurtijdschriften.nl/record/541086
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