Grass, Shrub, Grass… Tree! Measuring Regrowth in a Burned Forest

A black spruce sapling growing among grass in an area of taiga forest that burned in 2015. Credits: NASA/Maria-José Viñas


“Oh, and here’s a black spruce!” exclaimed Charlotte Weinstein, an assistant research scientist at Michigan Tech Research Institute (MTRI), while pointing at a delicate sapling barely the height of a thumb that was almost hidden among the tall grass.

Weinstein and her colleague Shannon Rose, a research fellow at University of Massachusetts-Amherst (UM-A), were painstakingly counting and cataloguing each plant growing in a one-by-one-meter square plot set up in a taiga forest in a remote corner of Canada’s Northwest Territories. The forest burned in 2015, and the wildfire left behind an austere landscape of blackened thin trunks sticking out from the ground, interspersed with patches of exposed limestone rock that had previously been covered by a thick mat of organic soil that burned during the fire.

Four years after the event, vegetation is growing again. But how different will it be from the original taiga forest? Will the new shrubs and trees and the reforming organic soil layer be able to store a similar amount of carbon? Will the changes in plant composition and soil moisture also affect the animal species dependent on the forest?

Charlotte Weinstein (right) and Shannon Rose catalogue all growing in a one-by-one-meter square plot. Credits: NASA/Maria-José Viñas

To answer those questions and more, groups of researchers from all over the United States and Canada are flocking to the Northwest Territories in summer 2019 to carry field work under the umbrella of NASA’s Arctic-Boreal Vulnerability Experiment (ABoVE), a comprehensive field campaign that probes the resilience of Arctic and boreal  ecosystems and societies to environmental change – including wildfires.

Weinstein and Rose worked together with Mike Battaglia (MTRI) and Paul Siqueira (UM-A), who took measurements of soil moisture and active layer depth (the top layer of soil that thaws during the summer and freezes in autumn) while the women counted plants. The researchers had all been doing field work for days when a small team of NASA communicators, including this writer, visited them in the field on Aug. 17; they still had about a dozen field sites to explore in the upcoming days. After sampling the burned area, the group moved on to a nearby swath of intact forest – in there, under the canopy of the intact trees, the carbon-rich soil was incredibly squishy and would sink under one’s steps, enveloping my hiking boots in bright green moss.

The active layer and soil moisture measurements were repeated in the unburned forest, but this time the researchers were also gauging plant biomass. Weinstein and Rose started measuring the diameter and height of all trees within a 10-by-10-meter square, while Battaglia dug a pit and extracted a large cube of dark soil to measure and take samples of the organic layers. Because the soil is frozen most of the year in the Arctic and boreal regions, the organic matter within doesn’t decompose. As a result, soils in those parts of the world often sequester more carbon than the trees and shrubs growing on them.

Mike Battaglia holds up a block of carbon-rich soil extracted from an unburned forest near Kakisa, Northwest Territories, Canada. Credits: NASA/Maria-José Viñas

After their field campaign, the team’s measurements of plant composition, biomass, soil moisture and active layer will become part of ABoVE’s  wealth of publicly-shared data.

“Our end game is to incorporate all field and remote sensing measurements into computer models to understand the long-term change of the land,” Battaglia said.