Pollution tolerant mosses

I have identified two of the mosses found on my walk to Red Barn Field yesterday. One is the common pincushion Dicranoweisia cirrata and the other bud-headed groove-moss Aulacomnium androgynum. The second of these does not have normal spore capsules but produces an upright stalk with a cluster of gemmae at the top. Gemmae are not spores or seeds, they are simply one or a small bundle of cells capable of developing into a new plant.

Interestingly both these mosses illustrate a similar point about the complexity of the changes we are visiting on our environment. Of the common pincushion Smith (2004) says “One of the few mosses that seems to be increasing, possibly because acidification of substrates reduces competition from other more pollution susceptible species.” On bud-headed groove-moss he says “has increased in parts of England, particularly in the last 40 years, possibly as a result of reduced atmospheric pollution and reduced competition from other epiphytic species unable to tolerate levels of pollution that still prevail.” Some pollutants, like sulphur compounds have decreased, while others, nitrogen compounds in particular, have increased and, in the latter case, are causing acidification.

REFERENCE: Smith, A. J. E. (2004) The moss flora of Britain and Ireland. Second edition. Cambridge University Press, Cambridge.