16 May 2013

Chasing bison: Smokin' grass

In the grand scheme of things, most prairies and forests in western North America historically burned far more often than they do today.  The nutrient cycling, clearing of young trees, and other disturbances caused by these fires are essential elements of many ecosystems.  In Prince Albert National Park, two species - a plant and a large mammal - are key drivers for conservation planning.  They are the reason the park sets fires each year.  

On May 9th, several meadows within our study area were burned, as part of the park's prescribed fire regime.  I was invited along to document the burns, which were carefully controlled, deliberate, methodical, and yet still managed to offer a few surprises.

The park's fire specialists test relative humidity, wind direction and wind speed pre-burn.

 Assessing the soil moisture content pre-burn; this spring, the soil was more wet than optimal for the depth and intensity of burns desired.  Basically, this just means the fires were weaker, and the grasses, trees and shrubs might not have been as seriously affected as the fire team would like.
 Plains bison (Bison bison) are one reason why the  grass gets torched.  Prescribed burning is done, in part, in order to conserve and enhance bison habitat in the park - some of their preferred forage species benefit from fire.  As the bison also graze a great deal in open areas, keeping the meadows open is critical.

The other species influencing the burn plans, plains rough fescue (Festuca hallii), is found in only about 6% of its historic area.  Fire is a key part of recovery efforts, because many regions where it once grew are now encroached on by aspen saplings, willows, and other trees and shrubs.  The park's prescribed burning is intended to expand the grasslands in the park to the size they were three generations ago.

Prepping the torches

 With the soil as wet as it was, and standing water in many parts of the target meadows, it was necessary to deliberately set fire to the shrubs on the edges of the meadows.

It is not difficult to understand why early homesteaders used dried bison scat (called bison chips, I believe) as fuel.  The scat in this meadow burned as if it were charcoal.

In areas where the fire did burn hot enough, the shrubs and trees will be set back several years.

Someone called these shrubs "bog birch," and boy howdy did they burn hot, belching clouds of thick smoke into the sky.

Starting a "back burn" line across a 
particularly wet spot in the meadow

Checking in re fire crew locations toward
the end of the first meadow burn

Dry old aspen, bog birch, and who knows what
all went up in flames as the fire approached a
small knoll separating the meadow from a large lake.
A couple small meadows caught fire, as did this stand of
aspen alongside a small pond tucked away in the woods.

A larger crew was responsible for the second burn
The crew leap-frogged, setting back burn lines,
every few yards (metres), across the meadow.

Once again, special effort was made to ensure the wet areas
and trees and shrubs along the meadow's edge all burned.
This final stand of dry old aspens and
shrubs cooked up a noteworthy smoke plume.

After the burns, both of the main meadows saw a lot of bison action within the first week.  Since then, we've seen a handful of bison in the larger meadow, but little to speak of for quite a few days.  On the other hand, the smaller meadow several miles away has been hopping with bison, a bear, fresh wolf tracks, etc.  Both meadows look like golf courses right now - so thick with freshly sprouted grass it's difficult to believe they were blackened only a couple weeks earlier.  It has been really neat to watch them grow back, track what species come in first, and to find which old trees fall in strong winds.

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1 comment:

fruit.root.leaf. said...

That's great, Brenna! I had no idea you were reading the blog. :) Come on up and burn something...Heather's on her way. At the very least, we could have a campfire. :)

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