Willow Creek History by Marcia Penner Freedman About the Author Fighting Fire in the Sierra National Forest Willow Creek History Marcia Penner Freedman

Willow Creek History

The Give and Take of Fire

That fire requires oxygen is something children learn early in life. A second grade science lesson, a jar placed over a flaming candle. The flame dies out. The wick smolders and cools. Heat, fuel, and oxygen – the fire triangle of the child’s science – has been fire’s story since its appearance on Earth, which according to fire historian Stephen J. Pyne, was  400 million years ago, when all the ingredients were in place and the triangle completed.

“Of fire’s three essential elements,” Pyne  writes,

only the heat of ignition thrived on the early Earth. Oxygen did not begin to collect until the last two billion years, and did not begin to approach modern quantities until roughly 500 million years ago. Land plants suitable to carry combustion did not become abundant until 400 million years ago. Before that time the Earth lacked the means to burn regularly or vigorously.

For 400 million years fire has followed a consistent principle: after ignition – which in the forest occurs naturally in the form of lightning – sufficient heat, fuel and oxygen must be present if fire is to take hold and thrive. The removal or reduction of any one of these elements diminishes or extinguishes the fire’s energy.

Fire Scars – Snapshots In Time

Someday you might find yourself standing by the stump of a two-hundred-year-old tree. If you are the type who likes to check things out, you’d probably begin counting the rings, the record of its age imprinted on the trunk.  And, it’s likely you’d stop if the distance between the rings narrowed and the counting became tedious, or when the rings swirled from a neat path and you lost your way, or when they bumped up against a chink or a stain.  Leave it to the experts you’d think, possibly not realizing that there is a field devoted specifically to tree ring counting: ‘dendrochronology’. 

For the dendrochronologist, a scientist who uses tree rings to date historical and environmental events affecting trees, it’s at the chinks and stains, and at the squeezed together, sidestepping rings where the fun begins.  Like an archaeologist, who reconstructs the story of a people from the excavated bits and pieces of their past, the dendrochronologist assembles the life story of trees. The glitches and discolorations, the spacing and swirl patterns of the rings offer clues to the tree’s annual ecological and climactic experiences. Was it a dry year or a wet year? Was there a period of drought? Bug infestation? Did this tree live through fire events, when and of what kind?

Fire scars are the tree’s messengers of fires past. They are the healed-over fire injuries etched into the timeline of the tree’s rings. They pinpoint the years a tree experienced fire, even hint at the fire’s severity. Dendrochronologists map fire scars. With fire mapping comes a glance backwards in time, a snapshot, so to speak, of a single tree’s historical bouts with fire, or of the patterns of fire episodes – regimes – that visited a patch of trees. Imagine mapping a two-thousand-year-old Giant Sequoia, or a grove of the giants. What a fire story that would tell.

Living with Fire

Experts tell us that wildfires are becoming more frequent and more intense. They say it’s not a matter of if, but when the fire will come.  So, in April each year we begin to anticipate the arrival of the fire season, almost expecting disastrous wildfires to happen.  In early summer as the air heats up – particularly in a year when the snowpack is down 50% and it hasn’t rained in three months – we begin watching for the telltale sky, when the sun will turn orange behind a shroud of brown haze. We wake up in the middle of the night and look out our windows, sniff the air.  Has a fire started somewhere as we slept? Fire talk has entered our conversations.  In coffee shops, at the supermarket we chat facilely about fuel loading and suppression, backfiring and cutting line.

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