National Geographic : 2003 Feb
Ihe Circle Unbroken After defending her nestfor as long as she can swim upright,a female sockeye salmon drifts back into an eddy to die, becoming a vital source of nutrientsfor the stream. The massive influx ofsalmon carcasses is the key to healthy riverecosystems in the region, eventually benefiting everythingfrom beetles to offshore orca populations. The more carcasses, the more insects hatchfor the rough skinned newt (above right), and the more animal droppingsfor the bananaslug (right), king of the decomposers. More than 800 of British Columbia's salmon stocks are at moderate to high risk of extinction or have alreadydisappeared,with much of the decline attributedto habitatdestruction. beetles, and other organisms slurping their way through the wooden carcass. The fallen tree also stores tons of water like a sponge, helping main tain the high humidity and moderate temper atures crucial to the life cycles of so many other species from liverworts to tree frogs. The cool, moist conditions of this western red cedar/hemlock zone also support a spec tacular diversity of fungi-several thousand species of mushrooms and molds. "Our rain forest is like a tropical forest turned upside down," said Bryce Kendrick, a fungi expert overseeing a research project in Clayoquot. "Instead of most of the action being in the plants, it's underground. There are several kilometers of fungal threads in a pinch of soil here." Many form symbiotic relationships with 124 NATIONAL GEOGRAPHIC * FEBRUARY 2003 the roots of vegetation. Known as mycorrhizal fungi, they collect moisture and nutrients via their own rootlike networks and pass them along to plants in return for some of their energy laden sugar. Plants invested in this kind of joint venture grow faster, handle environmental stress better, and enjoy higher rates of survival than those without. Often, the microscopic threads link plants belonging to entirely different species: small trees to larger ones with greater soil resources. In fact, nearly all vascular plants use fungi to tap into food collected by their neigh bors. Join this vast, hidden network, and you're tied into the forest in a whole new way-one that makes it harder than ever to say where the individual ends and the community begins.