Summer World_ A Season of Bounty - Bernd Heinrich [79]
17
Moss, Lichens, and Tweedlaarkanniedood
THE ROBINS AND THE PHOEBES ON OR NEXT TO OUR house hopped out of their nests, adult-size, at two weeks of age at the most. They were aided first by the warmth of a brooding parent, and then they warmed themselves by their own metabolism. The plants’ growth, stimulated by the warm summer days, was as impressive. Rachel kept track of what grew in the garden, and I was more focused on what went on outside it. On my daily jogs past a beaver pond I was especially impressed by how fast the stump shoots grew where the beavers had chewed off trees. Some ash shoots went up nine feet in a single season, and red maple shoots grew as much as sixty-six inches. They had been growing at a steady rate of almost an inch per day for the whole summer. Surprising as the fast growth was to me, I was even more impressed by how quickly it could come to a halt. Most trees stopped lengthening their twigs entirely by mid-June, when there were still three months of summer to come, but vines and some tree stump shoots (those in direct sunshine) kept right on growing at the same furious pace. Warmth and sunshine may translate into growth, but only if everything else is equal. In deserts there is plenty of both, but growth tends to be very slow.
Deserts are a source of marvels of survival in extreme summer, and so an extreme desert—one with the least water and the most heat—should be a place to find the most marvels of biological ingenuity. The Namib Desert along the Skeleton Coast of southern Africa provides examples of the exotic and the bizarre—silver ants, head-standing beetles, small plants that mimic stones to reduce water loss and avoid being detected by thirsty and hungry grazers, and a fern that can dry up and revive. The ferns that I knew about from Maine and Vermont grow in wet places, and when they run out of water they run out of life. But in the Namib I saw a fern that can dry and curl its fronds into a tight ball, and when wetted it uncurls and there it is—instant live fern, the “resurrection fern.” It is probably the perfect house plant, for me. But I never thought much about that fern until unexpectedly last summer in Vermont, when I turned our garden hose onto our serviceberry tree.
Our serviceberry (Amelanchier) tree is much like many others growing wild in the surrounding woods. We sometimes hang suet on it for woodpeckers and chickadees in the winter. Otherwise we pay no attention to it—except in May, when, several days before the trees leaf out, it erupts for a week in a mass of white flowers. That is also when the ground thaws, the time people used to bury the dead and hold funeral services here in New England (hence the serviceberry name). By June this tree bears purple berries (hence its other common name, Juneberry). Even before they are ripe, these berries already attract cedar waxwings, and then in late June and early July they also attract robins, along with rose-breasted grosbeaks, purple finches, wood thrushes, catbirds, veeries, tufted titmice, and cardinals.
In 2007 our summer, like most summers, had long dry spells. I got out the garden hose to water our serviceberry tree, remembering all the birds who feed there. I did not want its roots to dry up, because as with most plants, even a temporary absence of water kills. As I was idly spraying the ground beneath this slender tree I noticed for the first time what I had undoubtedly seen hundreds of times before: yellowish green moss on the rocks under the tree. Surely this moss would be totally dry! I bent down and peeled off a patch of it—dry indeed, dryer than a bone. I realized then that this moss was already many years old, and it must have been dry on many occasions during past summers.
I peeled off a handful of moss and put it into a bowl of water in the sun, and—presto—it soaked up water like a sponge; in seconds its slender fronds expanded and became vibrant green. It was just like the resurrection fern in the Namib Desert, which