The Shark and the Jellyfish: More Stories in Natural History

Where Nothing Grows

30 Where Nothing Grows In the midst of the humid low forest of eastern North America, gaps open out among the trees—places where, in contrast to the rank foliage all around, nothing grows. At the edges of these gaps, grasses and forbs compete for the space, backing up into the trees. But sunlight falling on the bare patches of wet soil in the open energizes no green leaves—the ground there is sterile. Under the surface the earth is boggy. Mats of plant matter have accumulated over the centuries and decayed in place, souring the soil until the decay process itself is slowed by the acidity. In this groundwater acid bath, the skeleton of a fallen animal—including the teeth—would dissolve without a trace in less than a season. Minerals essential for plant growth have been leached from the soil. Seeds that fall in these open spaces fail to germinate. These bare patches are a permanent aspect of flat, well-watered coastal lowlands. But the uncontested growing space in these sun gaps does not go unused. A few types of plants can survive in the nonnutritive soil. Most successful among them are the pitcher plants. The pitchers have developed a way to compensate for the lack of essential elements in the soil—they leach nutrients from the bodies of insects they have captured in the pools within their flagon-shaped leaves. Pitcher plants grow too slowly to compete with the tangle of greenery at the edge of these open spaces. But out on the marshy soil, where potential competitor plants die for lack of nutrients, they prosper and diversify. As the sun reemerges after heavy rains, the surfaces of their water pockets glint across the boggy depressions. Should a beetle slip off the treacherous lip above one of those little cisterns, or a water bug land on the reflective surface, it would immediately fall through the waterline. Its slowing, futile movements would fade into the depths of the digestive pool, eventually providing the pitcher with the sustenance to grow where little else does. Every pitcher plant is a self-sustaining microcosm. The little basin is home to a food chain based on bacteria and extending up to top predators, the larval stages of specific, coadapted midges and mosquitoes. The plant provides the trap that captures the prey, and the animals within each play a 31 part in reducing the bodies of those insects all the way down to the soluble nutrients that support the plant in which they live. To prevent the pool from becoming stagnant, the pitcher plant absorbs carbon dioxide from the water and infuses oxygen. A very different environment thousands of miles away shares one characteristic with the Eastern Seaboard—it contains a habitat where nothing grows save for a pitcher plant. This forested domain falls along the mountains on the border between northern California and Oregon. It is a sloping , rocky terrain of musical brooks, where bracing breezes sweep up out of nowhere in the middle of a calm day. Alpine meadows open out onto hundreds of square miles of dark conifers that carpet the slopes below the tree line, shot through with yellow veins of aspen as the brief summer wanes. One false step. A cricket explores the edge of a purple Sarracenia pitcher. 32 This realm grows as much biomass per acre of woodland and as much floral diversity per foot of trail as would be found in any tropical setting, reflecting the confluence of its three habitat zones—the granitic Sierra Nevada to the southeast, the metamorphic Coast Ranges to the west, and the volcanic Cascades to the north. Magnificent firs and cedars sigh in downdrafts flowing from the peaks; ospreys and pine martins keep watch through soaring branches; mariposa lilies and tiger lilies rise through carpets of fallen needles, sharing the understory with cobra lilies, which are not really lilies at all. Cobra lilies are slender pitcher plants whose hollow stalks are topped by a bulbous helmet that conceals the water column within. In profile, a cobra lily resembles an angry cobra reared up to display its inflated hood. An entrance through the underside of the helmet meets insects that walk up along a paired, leafy appendage reminiscent of a serpent’s forked tongue. The stalks of cobra lilies twist as they rise, so that clusters of plants with a common footing each face a different quadrant of...