The ecology of bryophytes is an interesting and diverse area of study. Bryologists in this field study the distribution of bryophytes, their relationships with other plants and animals, the roles that they play in an ecosystem, and much, much more. Here I will go over where bryophytes can be found and some aspects of why they are important.

According to most sources, there are 17,000 bryophyte species in the world which are found on every continent including Antarctica. Bryophytes can occur from sea level to alpine areas, and from temperate climates to the tropics. In fact, the only environment where they are never found is the ocean. Bryophytes differ remarkably in where they will grow. You will find them in sunny and shady areas; on rocks, tree bark, decaying wood, and litter; in streams, sea spray, or in dry prairie areas. In general though, most mosses and liverworts thrive in moist, shaded habitats. Some factors that influence where a given bryophyte species will occur are light, moisture, temperature, acidity, presence of other plant species, and substrate.

Many bryophyte species are widely tolerant of any conditions, while others are only able to grow in certain, very restricted, habitats. For example, there are some species that can only live on animal waste, and others still that only grow on a certain rock type. Bryophytes can be restricted to pristine natural environments, or they can be very successful on rooftops and sidewalks.

Despite their small size and inconspicuous nature, bryophytes are very successful and important parts of many ecosystems. They form critical relationships with other plants and animals, and are often vital for water and nutrient uptake, soil stabilization, and site colonization. Part of their success is due to the fact that they can avoid competing directly with higher plants, either because they live in areas where higher plants cannot exist, or because they are small enough to inhabit microhabitats that are not suitable for other plants. However, when needed, mosses can be excellent competitors despite their small size. This is due, in part, to the fact that they absorb nutrients and water through their leaves, often before these resources even make it to the soil where they would be available to vascular plants. Also, in some cases, the abundance of certain mosses on the forest floor will modify environmental conditions like temperature, pH and moisture, such that the habitat is even more suitable for themselves, and less so for higher plants.

Mosses and liverworts can carpet rainforest floors, and in coastal British Columbia they often comprise a significant proportion of the forest biomass. These carpets are sometimes formed from a variety of species that seemingly coexist peacefully. Other times, however, the carpets are monospecific mats that exclude other species. No matter the composition of these bryophyte carpets, they can be ecologically important. Areas covered in bryophytes provide shelter for some tiny organisms, food for others, and nesting material for birds. As such, a diverse array of invertebrates and plants rely on the presence of bryophytes.

The fact that bryophytes have no roots allows them to grow in areas without soil. They anchor themselves to their substrate using rhizoids instead, and take up water through their leaf cells. This lack of roots enables them to live on rocks, trees and other soiless substrates. In fact, bryophytes are often pioneers of inhospitable habitats like rocks and concrete. As a bryophyte grows on a rock, dead remains accumulate over time, which eventually decompose, creating an acidic environment that breaks down the rock surfaces. The decaying moss and particles of rock begin to form a thin layer of soil which eventually allows vascular plants to colonize the area.

Bryophytes can store large amounts of water, nutrients and carbon. In many ecosystems, especially peatlands, they function as carbon sinks, a virtue that is considered very important with the rise of global carbon dioxide levels. However, as global temperatures also rise, the carbon that has been sequestered from the atmosphere might be released from the plants and returned to the air in coming years.

References and Further Reading

Shaw, A.J., and Goffinet, B. 2002. Bryophyte biology. Cambridge University Press, London.

Schofield, W.B. 1992. Some common mosses of British Columbia, 2nd ed. Royal British Columbia Museum, Victoria, Canada.

The field museum Chicago. Bryophytes [online] http://biology.usgs.gov/s+t/noframe/j276.htm. [Cited March 20, 2006].

By Sharon Jeffery

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