2018-12-01_Discover

December 2018^ DISCOVER^27

CLOCKWISE FROM TOP: JIM PEACO/NATIONAL PARK SERVICE; COURTESY OF MONICA TURNER; PEACO

high temperatures, prolonged heat

and other conditions are lengthening

the burning season and making severe

ires more common, not only in the

park but also around the world. How

forests will cope is not clear. Turner

thinks the research produced after the

Yellowstone ires of 1988 can serve as

a benchmark for how forests might

respond to repeated burning, and

the hot and furious future that may

await them.

MORE FREQUENT FIRES

Climate change has been expanding

the ire season. A 2016 paper by

researchers from the University of

Idaho and Columbia University found

that rising temperatures have led to

an additional 16,216 square miles of

forest burning in the United States

between 1984 and 2015 — forests that

wouldn’t have burned otherwise. The

same researchers found climate change

led to nine more days of “high ire

potential” each year from 2000 to 2015.

These ires can burn forests that have

been standing for some time or reburn

forests recently incinerated.

Turner is concerned about the more

frequent ires that consume areas

previously charred, called repeated

short-interval ires. While the 1988 ires

burned old-growth trees, many between

100 and 250 years old, the ecosystem

was adapted to such ires. Repeated

short-interval ires, on the other hand,

are destroying younger trees, some

less than 20 years old. Different trees

produce cones and seeds at different

ages, so very young trees may burn

before they can produce viable seeds.

Some pine trees produce serotinous

cones annually, but not until they start

producing seeds. The lodgepole pine,

for instance, begins producing viable

seeds at 5 to 10 years old. These cones

stay on the tree from year to year,

increasing the tree’s seed supply, until

a ire erupts. Areas reburned before

the trees have had a chance to build

up their seed supply may have a more

dificult time recovering.

Turner and her team are studying

Young lodgepole pines grow in a stand of

trees killed by Yellowstone fires 10 years

earlier (above). These pines require the

heat of a fire to open their cones (below).

Ecologist Monica Turner has been studying

the recovery of burned forests at sites like

that of the Arnica Fire (right), which in

2009 burned around 9,300 acres.