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Nature’s Response to Wildfire

Nature’s Response to Wildfire

Aristotle was an intelligent guy. He is often credited with being the first genuine scientist in history. Not only was he smart, he was very observant and noted that nature is either at rest or is changing.

Fire, along with other natural disturbances such as floods, landslides and earthquakes, can generate substantial change across the landscape. Fire, one of nature’s oldest phenomena, has left its fingerprint in petrified wood and coal deposits that formed around 350 million years ago. Although some fires back then were probably caused by volcanic eruptions, most were likely started by lightning strikes.

Most of us have seen lightning crack out of the clouds and hit the ground, but did you know only certain bolts can start a fire? There are two types of lightning: hot lightning and cold lightning. A bolt of cold lightning carries an intense electrical current but only lasts for a few thousandths of a second. Hot lightning has currents with less voltage but can last as long as a full second. One second isn’t a lot of time, but it is long enough to start a fire. Today, about 10 percent of wildfires are started by lightning strikes; the remaining 90 percent are caused by humans.

Regardless of how a fire starts, the flames change the scenery. Last summer, several wildfires flared up in Northern Idaho; however, not nearly as many as the summer of 2015—one of the worst fire seasons on record in Idaho. Approximately 804,094 acres burned in Idaho in 2015, whereas in an average year about 577,700 acres are consumed by wildfires. Fires burn intensely in some areas while leaving other areas completely untouched, creating a patchwork of different habitats.

Some fires are tenacious and can burn until the rain and snow of autumn and winter finally extinguish the flames. In spring, as the Earth’s rotation slowly brings more sunlight, longer days, warmer temperatures and moisture in the form of melting snow and spring rain, we see another transformation, one not driven by infernos, but by new growth and regeneration. Nature, with patient persistence, will get to work with the business of restoring what was consumed by the flames, and doing it with grace and beauty.

Change brings opportunity, right? Fire provides the opportunity for regeneration and growth of plant species that are fire-dependent. For example, some lodgepole pine cones are sealed with resin (serotinous cones) that traps the seeds inside until the cone is subjected to the heat from flames, which melts the resin and releases the seeds from the cone. Plant species that are shade-intolerant take advantage of increased sunlight in fire-created canopy openings that allow seedlings a place to thrive and out-compete shade-tolerant species.

Burned vegetation and trees add nutrients to the soil that enhance plant growth, starting with those leafy herbaceous plants we call wildflowers and weeds. These quick germinating forbs take advantage of the new open ground and spring to life. For example, fireweed is characteristically the first to appear after the fire has past, often in a matter of days. This pioneer species quickly colonizes the slightly acidic soil left in the wake of a fire; thus, its name. Those long graceful stems with their burst of purplish-pink flowers are inspiring. And, as with Yellowstone National Park after the catastrophic fires in 1988, the Northern Idaho burn scars are likely to have a riot of wildflowers in the next two to five years.

Grasses, with their extensive root systems that have survived in the soil, start sending up shoots as soon as the spring rains moisten the ground. Additionally, many plant species like willow, aspen and birch will regenerate from their roots that survived the heat and flames underground. Seeds that survived in the soil are combined with others deposited in animal droppings and those that are blown in on the wind.

Fortunately for those of us who are wild harvesters, Morchella fungus survives wildfire through its extensive underground network of spider-web threads called mycelium that take in a rush of nutrients from burned vegetation and decomposing trees. The mycelium pushes fruiting bodies up above the soil creating a fairy forest of morel mushrooms. Local foragers are well aware of these morel “hot spots,” which can be successful hunting grounds for a year or two after a fire.

These pioneer plants gradually set the stage for insects to colonize the area and start providing food for birds and small animals, which, of course, provide food for larger animals. In a relatively short amount of time, the burn scar shows incredible beauty in the details of its reconstructed diversity. This mosaic of new and existing growth supports a wide variety of wildlife species. Deer, elk and moose will feed on new shoots of grass and shrubs. Birds of prey will hunt in the burned areas, particularly along the edge with unburned areas where they nest.

Dead and burned trees, called snags, may look lifeless, but often they are teeming with boring beetles and other insects. Woodpeckers focus on these snag forests to feed on the bugs and peck out nesting cavities. Other cavity dwellers, such as bluebirds and tree swallows, use these cavities after the woodpeckers move on. Seed-eating birds take advantage of the lodgepole pine seeds that have been liberated from the cone. And, all those wildflowers attract hummingbirds. Here again, change provides opportunity for some species.

As Mother Nature works to recover the landscape, we will witness many successional changes from one year to the next. Fires have been part of the natural scheme of things for eons, and in our corner of the world, they have historically been very common. Trees that survive a fire record the history of the burn. Trees add a new layer of cells each year (a growth ring) that increases the size of the tree. When a tree is scorched during a fire, the burn scar is eventually encircled in the next growth ring, leaving a record of the fire history. Plants that have adapted over time to fire are important players in nature’s recovery from disturbance as it progresses to a resting state again.

Nature’s ability to recover from disturbance is amazing, isn’t it? Aristotle put it simply, “In all things of nature there is something of the marvelous.” Looking at the different shapes, sizes and, in some cases, the unique structures of leaves on the deciduous plants alone is impressive. It is like taking a walk through a local art gallery and viewing the latest display of various artists’ work. And although it appears to us that nature is resting, change is still happening. There is some amazing photosynthetic work going on, and as a researcher trained in the scientific method, I acknowledge all of the evolution and microscopic cellular activity, but I prefer to just enjoy the marvelous, awe-inspiring magic of it all.

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