Gathering Moss by Robin Wall Kimmerer

Author:Robin Wall Kimmerer [Kimmerer, Robin Wall]
Language: eng
Format: epub
ISBN: 9780870716416
Publisher: Oregon State University Press

The foliage of D. flagellare would never be mistaken for the round shining leaves of Tetraphis. Each leaf is long and stiffly pointed, like a tiny pine needle. Its reproductive strategy calls for making sexual spores as well as asexual or clonal propagules. Rather than the lovely gemmae that Tetraphis splashes around the log, D. flagellare clones itself with little bristle–like tufts at the tip of each shoot. Theoretically, these tufts can break off, releasing individual “brood branches,” long thin cylinders of green, about a millimeter long. Each brood branch has the potential to clone a new plant. But potential does not always align with reality. In order to be useful, the brood branch would have to detach from the parent and somehow move to a new gap of bare wood.

Try as I might, I couldn’t see how that happened. I thought they might splash like Tetraphis gemmae, so I set up experiments to shower them with water. Nothing. Wind? I put sticky traps around the plants to detect any brood branches that might blow from the parent. Nothing. I added a strong fan to help matters along. Still nothing. D. flagellare makes clonal propagules but seems incapable of using them. Non-functional parts to organisms are not uncommon. Many organisms have vestigial structures that have lost their function, like the human appendix. Perhaps brood branches were similarly useless.

My student, Craig Young, and I spent two summers on hands and knees. Dead logs and their moss communities became our world. Each gap in the mossy cover of the logs was painstakingly described. Its moisture, light, pH, size, position, the trees overhead, and the mosses at the gap edge—all was recorded in our notebooks. Contrary to popular belief, blood sacrifice did not disappear with the dawn of science. The blackflies in May, the mosquitoes in June, and the deerflies in July all benefited by the hours we spent sitting still by logs, mapping out the pieces of the jigsaw puzzle. Craig became adept at grabbing our tormentors out of the air when they were flying away, heavily laden. His notebook was splotched with squashed flies and small spatters of our blood.

Our observations revealed a pattern so clear that I marveled at its constancy. While Tetraphis and D. flagellare both colonize gaps on dead logs, there is a marked separation between them, a segregation so complete you’d think there were “Tetraphis only” signs posted at the gap edges. Tetraphis was most common in big gaps, those more than about four square inches. The bigger the gap, the more Tetraphis. D. flagellare was restricted to small gaps, generally about the size of a quarter. Because gaps occur in many shapes and sizes on the log, apparently the two species could coexist by specializing. With Tetraphis in big gaps and D. flagellare in small ones, they could avoid competition.

This pattern directly mirrored the gap dynamics of the forest overhead. Tetraphis responded to big gaps, as if it had taken lessons from aspen, sending out lots of highly dispersable propagules, quickly cloning itself to fill the space.

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