Intensity of wildfires can actually change localized ecosystems

Days to years to regrow

The amount of time it takes an area to regenerate from a forest fire depends on the ferocity of the fire.

Many grassland plants have adapted to light to medium fires and can begin to re-grow in a matter or days. Some fires even activate seeds that had been lying dormant on the ground.

Mathieu Bourbonnais, an assistant professor in the department of Earth, Environmental and Geographic Sciences at UBC Okanagan, says wild plants have evolved over the years to deal with fires.

Many grassland plants have deep root systems that are not impacted by surface fires and can quickly regenerate, which was seen at a wildfire at the south end of Vernon, where green plants were sprouting a week after the fire was put out.

Dormant seeds are also found in the top layer of soil that are waiting for an event like a light fire to come through and burn their outer husk, allowing the seed to grow.

Bourbonnais says bunch grass, like that found in the Okanagan, is “really fire adapted.”

Areas that can regenerate quickly provide good habitat for a range of woodland creatures, from herbivores to predators.

The regrowth creates more forage opportunities for deer and bears as it creates new shrubs and berries for them to feast on.

However, a more intense fire can burn deeper into the root system, slowing regrowth.

“Fire size is not a good indicator of the impact a fire might actually have,” says Bourbonnais, adding the severity of the fire is more of a determining factor. A very hot fire could actually change the landscape.

“When a fire burns quite deeply through the organic layer, sometimes you don't get regeneration,” said Bourbonnais. “It can actually burn through the whole seed system and root layer.”

“In some cases, we can actually see systems shift a bit. Lodgepole pine and ponderosa pine are really fire adapted, but a high-intensity fire can burn through the cones and the seed source, so you might see another species move in.”

The intensity of the fire can change from one area to another as well, creating a patchwork of different flora.

“With a big fire, it is hard to say what will happen because there are areas that burned with high severity and low severity,” said Bourbonnais.

In some cases, it could take decades for an area to regrow.

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