Synopsis
The book consists of five chapters: Birth, Taking Root, Growth, Maturity, and Death. The book opens with an Acknowledgments and an Introduction section, and closes with Selected References and Index. In the introduction, Suzuki describes the tree at his home and the series of ideas and events that led to the writing of the book. Along with the narrative of the tree's life, the book includes digressions into related topics, such as the history of botany and animal life in the forest. The tree written about in the book is not any specific Douglas-fir, but rather a generic one.
The first chapter, Birth, begins with lightning starting a forest fire. The heat dries the Douglas-fir cones enough for their scales to spread and release winged seeds. Rain water transports one seed to a sunlit area with well-drained soil. Rodents and insectivores, whose food stashes were destroyed in the fire, eat truffles, which survived underground, and leave feces containing nitrogen-fixing bacteria in the soil. Following one dormant winter stage, the seed begins to germinate.
In the second chapter, Taking Root, the embryonic root emerges through a small opening in the seed coat and through cell division, aided by plant hormones, it grows downward. Water and nutrients enter the root by osmosis and are transported to the seedling. A symbiotic relationship develops between the roots and the truffles. The roots give its extra sugars to the truffles, which it uses for energy, and the truffles assist the roots' uptake of water and nutrients. From excess starches and nutrients gathered by the root, a stem similar to the root but surrounded with thin, grayish bark, grows upwards. As the starch reserves are exhausted, its first needles sprout and photosynthesis begins. The tree anchors itself with a deep taproot and a web of roots begin to grow laterally. Some roots develop symbiotic relationships with near-by red alders which excel at nitrogen-fixation but lack the storage capacity that the Douglas-fir can offer. In early April of every year, a new layer grows between the bark and wood. As this new layer takes over transportation of fluids throughout the tree, last year's layer of cells die and form a ring in the wood.
After about 20 years, the tree begins to develop fertile cones. Buds form where auxins accumulate; these become either new needles or cones. The buds remain undifferentiated until July and continue to develop throughout the fall and winter. The next year, some buds will open in mid-May exposing a new set of needles. The cone buds on the lower end of the tree while other buds burst open in April releasing a mist of pollen. The cones at the top of the tree open their scales for wind-borne pollen to enter. Within the cone, the pollen fertilizes a seed which is released in September. The quantity and quality of seed production varies year-to-year but a particularly effective crop is produced about every 10 years. Less than 0.1% of seeds survive Douglas Squirrels, Dark-eyed Juncos, and other seed-eating animals.
Over the centuries, the tree grows thicker and taller as successive rings develop around its trunk and new buds grow on the branches. The tree becomes part of an old growth forest with a shaded and damp understory of broadleaf trees, shrubs, and ferns. In the canopy, a mat of dead needles and lichen accumulate on the wide upper branches. Exposed to light, air, and rain, the needles decompose and the mat becomes colonized by insects, fungus, and new plants.
In the opening of the final chapter, Death, the tree is 550 years old and stands 80 meters (260 feet) tall. Under the weight of too much snow accumulating on the canopy mat, a branch breaks off. Stresses from a long winter with a dry summer weaken the tree's immune system. The exposed area where the branch broke becomes infected with insects and fungus. Insect larvae eat the buds and the fungus spreads into the middle of the tree and down to the roots. With its vascular tissue system compromised, the tree diverts nutrients elsewhere, resulting in needles turning orange on the abandoned branches. Death takes years to occur as successive parts are slowly starved of nutrients. As a snag, it becomes home to a succession of animals, like woodpeckers, owls, squirrels, and bats. Eventually the roots rot enough that a rainstorm blows it down. Mosses and fungi grow on the deadfall, followed by colonies of termites, ants, and mites, which all help decompose the remaining wood.
Read more about this topic: Tree: A Life Story