Grady Wayne - Tree : A Life Story.

Trees warp time.

JOHN FOWLES, The Tree

Alightning bolt illuminates the sky, striking the highest point of the forestedridge. The fire does not start at the top, however, where the trees are young andstrong, but slightly lower down, where over the years snags and fallen branches haveaccumulated to form a stack of dried kindling. One standing snag smolders for days,dropping live embers onto the rocky soil beneath it. The coals spread into the surroundinglitter and ignite a ground fire, which enflames small twigs and dropped cones in itspath. The fire licks up and tickles the lower dead branches of the living trees, quicklyascending the ladder of interlaced branches into the resinous middle story, whereit burns with such fierce intensity that it consumes all the oxygen in the surroundingair and reaches a temperature well above the flash point of living wood. Then, likea suddenly opened damper in a firebox, a charge of fresh oxygen borne in by the opportunewind is whipped by atmospheric convection, and all the flames in the world seem instantly,as if by some devilish magic, to explode into the forest canopy. What started asa ground fire is now a crown fire, which is a fire on the move.

The crown fire advances by sending scouts ahead of it, looking for fresh resources.First the main fire begins to wave back and forth, as though uncertain of what toconsume next; then its tendrils twist into little ringlets of flame, spirals andwhorls and mini-tornadoes, which soon combine to form one huge, angry vortex, a whirlingsilo of rolling smoke. The gases at the top, burning at temperatures in the rangeof 1000C (1800F), are sucked down to the bottom, where they pick up burning branchesand sometimes entire logs and carry them up the updraft enveloping the silo, whichnow acts as a cannon and fires them hundreds of meters into the unburned forest. Theair is filled with flaming missiles. Their mission is to start spot fires, or satellitefires, which then merge before reporting back to the main fire.

When the space between the main fire and the united spot fires becomes hotter thanthe flash point of wood, and is fed by the wind with its burden of fresh oxygen, suddenly,in milliseconds, there is no distinction between the main fire and its colonizingscouts. This is called a blowup. A fire that has been slowly advancing suddenly occupiesa hundred square kilometers (40 square miles). It no longer moves linearly; it isa spreading wildfire. The whole forest is a chaos of flame-laced smoke and searingheat, of animals and birds screeching and blundering in the dark, of loosened bouldersand roaring winds and the seeming end of all living things.

When every last stick of flammable material in the area has been consumed, when theground has been stripped of vegetation and sterilized of organic nutrients, wheneven the water has evaporated from the creek beds, when the rocks have cracked andsmoke and particulates from the fires burning have spun up to the very limit of theEarths atmosphere, the juggernaut of fire moves on, following fresh scouts to exploitnew territory in whatever direction geography and the wind determine for it. Whatit leaves behind is silence. The hissing and the roaring have departed; there areno animals, no birds or reptiles or insects, no wind in the willows, no rattle orscrape of branch on branch. No movement. No color but charcoal and ash gray. A personlooking upon such a desolated scene would be forgiven for thinking that fire is ascourge from the nether regions that Dante, writing halfway across the world aroundthe time that our fire erupted, called the Inferno. Rain comes from heaven; fire comesfrom hell.

SUCH A PERSON would be wrong. The west coast of North America, where this fire tookplace, has experienced such conflagrations regularly. The really huge fires, the centuryfires, swept through the northern forests every two hundred to three hundred years;smaller ground fires blazed as often as twice every three decades. Since the big trees,the mature Douglas-firs, the Sitka spruces, and the giant sequoias, live for morethan a thousand years, it follows that they are not consumed by even the biggestfires. In fact, big trees depend on big fires to advance and complete their life cycles.

In recent years, as a result of global warming, the frequency of wildfires on theWest Coast has soared exponentially. Instead of a ground fire cleansing the forestevery few years, there are now hundreds of such fires every year. And the numbercontinues to grow: in 2011, for example, there were 646 wildfires reported; in 2013,there were 1,851. In 2016, a comparatively wet year, there were still 1,050 fires.Also, because of hotter, drier summers, the extent of these fires has increased.Even in a below-average year such as 2011, the total area consumed by fire was threetimes the average, at 330,000 hectares (815,445 acres). Nearly half of all firesreported now are caused by human activity, some accidental, many deliberately set.We are, in innumerable ways, changing the nature of the planet.

The great natural fires come from neither heaven nor hell. They are part of the naturalprocesses that govern the life of plants and animals. Fire is energy that originatedin the immense cauldron of nuclear fusion that is our Sun. Solar energy streameddown on Earth and was captured by leaves and then transferred into stable moleculesthat are regularly, if accidentally, reignited and transformed back into fire. Thiscentury fire is as much a part of the life of the forest as rain, or the hum of insectsor the chirr of northern flying squirrels and red tree voles.

Lodgepole pines, giant sequoias, and other western conifers are serotinous, or lateopening; instead of dropping their seeds as soon as they are ripe, as apple and mapletrees do, they hang on to them and drop them in response to some environmental trigger.Lodgepole pines may keep their cones closed for fifty years, waiting for a fire tocome along to open the cones and release the seeds. Sequoias also keep their conestightly shut for decades, releasing the seeds only when the cones are heated to 50to 60C (120 to 140F), and such temperatures can only be achieved by fire. Plant(and animal) tissue begins to break down at 50C (120F), which means these giants release their seeds at temperatures high enough to kill them. It is thoughtthat the lowest branches on some conifers die and remain attached to the tree forno other purpose than to act as fuel to send ground fires shooting up into their crownsto heat the cones and spring the seeds.

After the fire

The ability to withstand intense heat is a valuable attribute in areas with whatis called a fire climatelow annual rainfall (less than 125 centimeters, or 50 inches,per year) with long, hot, dry periods and strong winds. Australia has such a climate,and its characteristic eucalyptus, or gum, tree is one of the most flammable treeson Earth, producing large quantities of dry leaves and even a flammable gas that canshoot flames a distance of 100 meters (300 feet). Yet gum trees can withstand incredibletemperatures, and some species even seem to need fire to remain alive. Even in relativelymoist climates, fire resistance can be an asset. In Hawaii, for example, the ohialehua tree (Metrosideros macropus) can actually be buried alive under a pile of burningcinders from a volcano and still send out fresh shootsit will even produce new rootsunder its pile of fresh ash.

Douglas-firs (Pseudotsuga menziesii