Thursday, March 20, 2014

Winter: The other growing season

Written February 27, 2014, published March 20, 2014. All photos by Kathleen Sayce.

As hardwoods break bud in late winter, the winter-growing season for a different biotic group winds down. These species grow all winter in faint light and ample moisture, and will be going dormant soon. These include mosses, liverworts, lichens, some ferns, algae and bacteria. All share a counter-season lifestyle––they grow and reproduce during the fall-spring period, and are dormant during the spring-fall period.

Orthotrichum lyallii is a dark green moss that lives on hardwood trees and shrubs, and forms distinctive loose tufts. In some old orchards, every branch supports multiple tufts of Orthotrichum lyallii.

Our area is part of the coastal temperate rainforest, a place that has so much rain that smaller plants live on bigger plants and other elevated surfaces and thrive with no connection to soil. The coastal temperate rainforest stretches from southeast Alaska south to northern California, in a long narrow band along the coast, with a smaller parallel band in the Cascades of Washington and Oregon.

Bigleaf Maple, Acer macrophyllum, is often covered with epiphytes, as seen here at Ft Columbia State Park. Ferns, mosses, lichens and liverworts cover the main branches and trunk of this maple tree.

The largest member of this winter-growing group is Polypodium glycyrrhiza, licorice fern, which puts out new green fronds every fall, and dries down in spring. In other parts of the world, species in this genus are often called 'resurrection ferns' because most put out new fronds in fall, and go dormant in spring. Licorice fern has sweet, anise-flavored rhizomes, hence its specific name, glycyrrhiza, which means 'sweet root'.

Licorice fern, Polypodium glycyrrhiza, grows new bright green fronds each fall. This luxuriant clump grows on big-leaf maple at Ft. Columbia State Park.

Equally striking are a group of epiphytic lichens, light green in color, which wither down to nubs and twisted brittle fronds in summer, and in winter burst into luxuriant growth. Common on hardwoods, especially fruit trees, maples and alders, they light up the garden as they reach maximum size in late winter. They aren't parasitic, just opportunistic, looking for a supporting tree to live on. In my yard, the supports are plum trees. Lichens are combined organisms, a fungus and an alga growing together.

Many clumps of Usnea spp. grow on a plum branch. In late winter this lichen festoons Pacific crabapple, apple and plum orchards, alders, willows, and other hardwoods. 

The light, bright green mosses that grow in lawns spend the summer being shredded and spread around lawn areas by mowers. Those tiny bits are ready to take hold and grow as soon as the days grow wet and cool. By spring, these mosses have grown into thick loose mats of fine green foliage, burying turf grasses under their luxuriant growth. Give them a few years to grow unchecked, and all the grass plants are gone, shaded out by the mosses. Last year I cleared mosses out of a lawn area by rolling up sections like carpet, and found that for every square foot of moss cleared, one or two scrawny grass plants remained. I reseeded, but it's a futile action. This area of lawn is too shady even in summer, too wet in winter, for anything but mosses to thrive. Likewise, the roofs that looked clean last summer now sport green clumps of mosses and the occasional gelatinous algal mass.

Homalothecium aeneum is a distinctive bright copper-gold color; it lives on trunks and branches of hardwoods, such as the trunk of an apple tree. 

In the dunes by late winter are luxuriant soil crusts, a mix of lichens, algae and mosses. They wake up and grow each fall, in dense multi-layered multi-species carpets that can be more than four inches thick. By summer, all that will remain is a thin, brittle blackish crust that will snap when you walk on it. Likewise, mosses that prefer open soil start growing in fall, and what you thought was bare ground is a green carpet by midwinter. Sometimes it seems like it happens overnight, but the young mosses were there all along, ready to spring into growth as soon as the air temperatures cooled off, the rain came back, and the light levels dropped.

Porphyra rediviva lives in salt marshes during the winter months, anchored to the tips of marsh plants. Brownish red in color, it is related to several seaweeds grown for nori. 

In the salt marshes there is an alga, a seaweed, that grows in winter and dies back each spring. This seaweed is Porphyra rediviva; it looks like an olive-brown-black mass, not alive let alone photosynthetic. For decades it was thought to be flotsam, loose and dying Porphyra fronds that had drifted in on high tides and stranded in salt marshes. A few years ago a botanist realized it was living, that its preferred habitat was salt marshes, and that it grew only during the winter months. Other red Porphyras live on rocks, such as at Waikiki Beach during the winter months, and disappear as spring approaches.

Neckera douglasii is very light green with undulate [transversely pleated] leaves; it grows on trunks and branches of trees and shrubs. This clump is growing on an old lilac trunk. 

As the days lengthen, while wet weather continues into spring, the mosses and lichens are actively growing. In a few weeks the sun will be strong enough and the weather drier. These cryptic small organisms will go dormant for another dry season. When fall rains and short days return, they will begin growing once more, the small plants that live on a schedule that runs counter to flowering plants and trees.

Ulota megalospora grows in tiny clumps, and its leaves twist into distinctive tips. Like Orthotrichum, this Ulota prefers twigs, stems and trunks of hardwoods.

Ramalina tufts often mix with Usnea on branches. Ramalinas have flattened branches, where Usneas have rounded branches. This tuft is growing on wood fence slats; other smaller lichens also grow on the slats, including Parmelia and Physcia.