I visited a nursery this afternoon and noticed an abundance of weedy bryophytes populating the tubes displayed under shade cloth. The most common were Fire Moss (Funaria hygrometrica) and Broad-lobed Marchantia (M. berteroana). Redshank (Ceratodon purpureus) and the introduced Common Marchantia (M. polymorpha) were also present. One that was missing, but which can be a big pest in nurseries, was Golden Thread-moss (Leptobryum pyriforme), which is probably introduced. All of these bryophytes are pioneer species that quickly colonise burnt ground. So, why do they crop up in plant pots? The potting mix often contains crushed charcoal. Charcoal is used because it improves drainage, absorbs salts and other impurities and sweetens the mix (prevents it becoming too acidic because of the organic matter components). Potting mix has abundant nutrients and is watered regularly. Nearly perfect! Pioneer species produce abundant spores that readily colonise bare surfaces, but they can also persist if the nursery does not have good hygiene practices, such as carefully washing and sterilising both pots and potting mix components. It comes as no surprise that these fast growing species all have symbiotic relationships with cyanobacteria, which can convert gaseous nitrogen to organic nitrogen compounds. The two mosses also have partnerships with mycorrhizal soil fungi. Spores of the cyanobacteria and fungi readily colonise potting mix as well.
Posted on: Thu, 18 Sep 2014 12:36:18 +0000
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