Sunday, September 1, 2013

Of Mosses and Mountains, I (recommended reading)

Moss with sporophytes growing on brick.
“Mysterious and little-known organisms live within reach of where you sit.  Splendor awaits in minute proportions.”  E.O. Wilson, by way of Robin Kimmerer.
I’m a summer reading underachiever.  I finished only five books before our public library’s program ended.  But quality made up for quantity.  Among the five were two excellent natural history books including Gathering Moss by Robin Kimmerer, about the diminutive fairy-tale-like world of mosses.

Mosses are small, as Kimmerer emphasizes right away, and the reasons and implications are fascinating.  First, most of us bigger folk ignore them ... including myself, a botanist. The plants of my world are vascular and generally grow at a scale that’s easy for me to experience.  Mosses are not; without vascular tissue they can’t transport water and nutrients very far at all, nor can they make the support structures that would enable them to grow tall.  So they live as tiny little plants in an enchanting world, which Kimmerer ably and entertainingly describes.
The enchanting world of mosses.  Kunstformen der Natur, plate 72: Muscinae by Ernst Haeckel, 1904.
Being small has advantages.  Mosses can inhabit the narrow boundary layer just above a surface, where any irregularities, including the moss plants themselves, slow the air and trap heat and moisture.  Those moss mats on downed logs have created their own greenhouse of sorts.  Even better, in the stillness of that thin layer the waste products of decomposers accumulate and benefit the mosses:
“the boundary layer can provide not only a favorable microclimate for moss growth, but also an enhanced supply of carbon dioxide, the raw material of photosynthesis.  Why live anywhere else?”
Pattern of air flow over a moss carpet.  From Gathering Moss.
Reduced water stress in the boundary layer is especially important because moss “leaves” are only one cell thick, with no protective cuticle.  That’s why we often find them where it’s shady, cool and moist, for example on the north sides of trees, or on rock outcrops along a mountain stream (below).
  Moss “branches” less than 1 cm long, moistened by spray from creek.
At the same time, mosses are tough pioneers.  Think about it.  Where do we see them? -- on downed logs, bare rock, brick walls, gravestones and other open or disturbed habitat.  Once established, they can trap dispersing seeds and provide suitable habitat for germination.  Eventually an entire community of plants may develop where once there was just a patch of moss:
“Aimee and I would rest on hot afternoons in a little grove of aspens that had somehow gotten started in this desolate place [mine tailings] that everyone wanted to cover in garbage.  We know now that these aspens originated from seeds caught on a patch of moss, and the whole island of shade began to grow from there.  The trees brought birds and the birds brought berries ... which now blossom around us ... sheltered from the harsh conditions of the mine, a few maple seedlings were holding their own.  Brushing aside the leaf litter, we uncovered the remnants of Polytrichum [moss], the first plants to begin healing the land, making it possible for others to follow.”
And there are creatures in the "moss forests" -- huge numbers of them.  The diversity and abundance of invertebrates in tropical forest mosses is astounding:
“One gram of moss from the forest floor, a piece the size of a muffin, would harbor 150,000 protozoa, 132,000 tardigrades, 3000 springtails, 800 rotifers, 500 nematodes, 400 mites, and 200 fly larvae.”
Why so rich?  Those apparently simple little mosses that we see actually are quite complex from the perspective of invertebrates, with a great diversity of habitats.  And those habitats are moist.  Could it be that the early stages of insect evolution, from aquatic to terrestrial, took place among mosses?

Not surprisingly, Kimmerer is a staunch advocate for mosses, and as it turns out, they need advocates.  Over-harvest increasingly threatens to wipe out mosses over large areas. Oregon Green Moss and other such products may sound wonderful and even eco-friendly, but the material that lines flower baskets, airport concourses and “wherever Mother Nature’s touch is wanted” comes at a cost.  Huge amounts of epiphytic mosses are harvested illegally in the Pacific Northwest.  While the legal quota is 230,000 kilograms per year, the actual take is estimated to be thirty times that.  Might moss awareness help?

Being a natural history geek, I find moss stories enchanting in themselves, but I also was taken by Kimmerer's writing.  She's a bryologist; moss research is her thing and her stories are largely science-based.  They are clear -- easy to follow and understand.  But equally appealing is her way of writing with wonder and awe and mystery, and of inspiring those feelings in the (this) reader.  I've always found mosses, with their miniature worlds and magical names, to be suggestive of fairy tales and perhaps even the abode of fairies, elves and goblins.  Kimmerer's explanations of moss biology and ecology don't detract from these feelings at all.  Of course I don’t really believe in fairy-tale worlds, but I’d sure like to!  Perhaps one day I will find one, if I pay closer attention to mosses.
The luminous Goblin’s Gold (Schistostega pennata), growing down a rabbit-hole!

What about those mountains in the post title?  They are the The Mountains of Saint Francis, by Walter Alvarez.  This is the other highly-recommended book I read this summer, and the subject of a post coming soon.

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