Wednesday, May 1, 2013

Sing a song of Sphagnum

For a plant, there is one good thing about being small; it’s a lot easier to get everywhere- for your seeds, that is. Nowhere is this more evident than where all plants are really small- the Arctic tundra.

The northern latitudes are covered by vast expanses of tree-less terrain covered by mosses and lichens that, for the most part, are the same around the world. Biogeographers believe that this similarity is facilitated by the small size of the spores of these organisms. The spores are 20-40 micrometers long (it would take about 500 spores to stretch across a dime) and can easily get picked up by the nearest breeze and transported thousands of kilometers. Upon landing, they germinate and grow into a new baby mosses and lichens. With frequent enough inter-continental exchange of spores, tundra looks like tundra looks like tundra.

Although spores are small and scientists think they travel great distances, testing this is actually quite difficult. How many spores actually do make the trip thousands of kilometers across oceans to new continents?

A scientist at Uppsala University in Sweden went out and measured how many spores of Sphagnum moss could be found at different distances from peat bogs (where Sphagnum and bog mummies live). Although 20 million spores were produced in every m2 of bog, only 6 million made it up into the air and just 4% of these managed to travel 40 meters away. Despite this rapid decline with distance from the bog, some spores are able to travel great distances. On Svalbard, the cloth spore traps showed that 1000 spores are deposited per m2 every growing season. And this is on a barren island 820 km north of the nearest Sphagnum bog (in Norway).

Oddly enough, the spores that made it to Svalbard and other islands were larger than the spores found at sites closer to bogs. Evidently, for Sphagnum, getting smaller is not a recipe for getting farther, and past a certain point, size really doesn’t matter.

You can find this article at:

ResearchBlogging.orgSundberg, S. (2013). Spore rain in relation to regional sources and beyond Ecography, 36 (3), 364-373 DOI: 10.1111/j.1600-0587.2012.07664.x

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