Thursday, June 25, 2015

Lichens at the Well

Crustose lichens on granite
Consider for a moment, the harsh physical conditions that plants must contend with on a bare slab of granite. How do they get water? How do they anchor themselves? How do they secure nutrients? In combination these factors create a formidable array of conditions, so tough in fact that only one group of plants in the entire world - the crustose lichens - have been able to overcome them....Tom Wessels, The Granite Landscape

Relatively simple pioneers
Once their 'spores' attach to new terrain it takes at least a decade of growth before crustose lichens become visible to the naked eye. A succession of colonization may ensue that after half a century creates conditions capable of supporting  foliose lichens. When  primordial soil with sufficient water-holding and nutrient capacity accumulates, fruticose lichens may follow.

Lichens on the old well
The old well harbored the greatest variety of species that Martha Finta and I encountered on our lichen expedition around Halibut Point State Park.

Examining lichens on granite
With a field guide we were usually able to place our discoveries within a genus, but exact identification proved more elusive because of close similarities among species. In a later visit to Harvard University's Farlow Herbarium Martha reviewed my photographs with associate curator Michaela Schmull. They decided that precise identification would require further testing in situ or bringing tissue samples to the lab. So my captions offer will refer to probabilities rather than certainties.

Foliose lichens succeeding crustose lichens
Nevertheless - the progressive colonizations form a landscape in miniature as beautiful as the broader surroundings.

'Maritime sunburst lichen' xanthoria parietina harmonizing with minerals
Martha recognized that the roof over the well would make for prosperous lichen hunting.
Martha Finta follows a hunch
At the edge of the roof a fleshy light green growth demonstrated how luxuriantly foliose lichens can grow on a substrate that holds moisture.

Foliose lichens on woody substrate
The shingled  medium radically condensed colonizing time and presented a gallery of ornaments from the lichen world.

Various foliose lichens
Conditions favored fruticose lichens in hospitable crevices.

Cladonia cristatella, 'British soldiers'

Another cladonia lichen, on the grotesque side

British soldiers adjacent to probable flavoparmelia species
Each type of lichen evolved as members of the ascomycetes group of fungi developed the ability to grow around photosynthesizing cells of various cyanobacteria or algae - which although usually regarded as different primitive plant types, may actually be a continuum of single-celled green plants. The lichen propagates itself by 'fruiting' as miniscule balls of fungal tissue surrounding a few of those green plant cells, carried to new surfaces by wind, water, or animated energies.

Crustose lichen, fruiting
The lichen partnerships colonize sites on every continent where the component plant groups cannot take hold by themselves. They extend the biosphere to areas of extreme exposure too barren to sustain 'higher' life. Like very few other organisms they endure drought in extended dormancy until precious water revitalizes their organic pulse.

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