The slope above Concow looks, at first, like an abandoned chessboard. Black trunks stand in rough columns where the white firs used to be. Between them, a low green carpet of bear clover and young ponderosa pine reaches up to about the knee.

Dr. Hannah Choi parks her truck at the edge of the forest road and pulls on a pair of leather gloves. It is 7 in the morning and the May light is already warm.

Choi is a fire ecologist with the United States Geological Survey, based in Sacramento. She has been visiting this particular hillside, a four-hectare permanent plot established by her predecessor in 1998, every spring since 2019. The plot lies inside the burn perimeter of the 2018 Camp Fire, the wildfire that destroyed the town of Paradise and killed eighty-five people in November of that year.

The fire reached this slope on the afternoon of 9 November. It moved with such speed that the canopy ignited before the understory had finished burning. The white firs, Abies concolor, which had dominated the upper slope for at least a century, were killed almost entirely.

Choi's plot held 142 white firs in the 2017 inventory. The 2019 post-fire survey found three living.

She walks the southeast transect first. The dead trunks are still standing, mostly, though several have fallen in winter storms. She measures the diameter at breast height of each, notes its lean, and photographs the base. The data feeds into a long-running study of standing dead tree dynamics, led by Dr. Robert Powers and the Pacific Southwest Research Station.

White fir is a curious species in Sierra fire ecology. It is shade-tolerant, slow-growing, and not particularly fire-adapted. Its bark is thin. Its branches reach low to the ground. In a frequent-fire regime, the kind that prevailed in the Sierra Nevada for thousands of years under Indigenous and lightning ignitions, white fir was kept in check.

A century of fire suppression changed this. White fir invaded the understory of mixed conifer forests across the Sierra. By the 2010s, in many stands, it had become the dominant species by stem count, often four or five times more abundant than the ponderosa pines and sugar pines that had previously held the canopy.

When the Camp Fire came, the white firs burned hot and they burned fast. Choi's plot recorded canopy temperatures, inferred from heat-cracked rock surfaces and consumed branch diameters, of over 800 degrees Celsius.

“When the Camp Fire came, the white firs burned hot and they burned fast.”

The question Choi has been asking since 2019 is what comes back.

The first answer, in 2019 and 2020, was bear clover, Chamaebatia foliolosa, a low aromatic shrub of the rose family with a thick rhizomatous root system that survived the fire intact. By the second post-fire spring it covered nearly forty percent of the plot.

Bear clover is locally called mountain misery, because it sticks to dogs and pants and smells, depending on one's mood, either of menthol or of a bad memory.

In 2021 the first ponderosa pine seedlings appeared, germinating from cones blown in from a small surviving seed source on the ridge above. By 2023 they were knee-high in places. By 2026 the tallest are over my head, Choi says, and gestures at a sapling that is taller than she is by several inches.

White fir, by contrast, has not returned in any quantity.

Choi has recorded sixteen white fir seedlings in the plot since 2019. Three remain alive. The species requires a more sheltered understory than the post-fire slope currently offers, and its seeds do not travel far.

She is not, she clarifies, sad about this.

The forest that is regenerating on the slope is closer in composition to the forest that grew here in 1850 than the one that burned in 2018. More pine. Less fir. More space between trees. A pattern of regeneration that, if subsequent fires are of moderate intensity and well-timed, could produce a stand that is more fire-resilient than its predecessor.

Dr. Hugh Safford, an ecologist at the University of California, Davis, who has written extensively on Sierra Nevada fire history, has called this kind of post-fire regeneration the beginning of forest reassembly. The word is deliberate. The forest is not coming back. A different forest is being assembled.

Choi works with a small team. Her field assistant, Maria Trujillo, walks the northwest transect with a tablet, recording shrub cover by species in two-metre quadrats. A graduate student from UC Berkeley, Theo Liang, sets up a remote camera at the corner of the plot to monitor large mammal use. Black bear, mule deer, and coyote have all been documented in previous seasons.

A new finding, included in Choi's 2025 paper in Ecological Applications, is that the regeneration is patchy in ways that correlate with pre-fire forest structure. Areas that had been thinned by the US Forest Service prior to 2018 are regenerating faster and with a more diverse mix of conifer seedlings.

The implication, Choi argues with characteristic caution, is that pre-fire forest management matters not only for fire behaviour but for what grows back afterward.

The data has been used, with some controversy, in support of expanded mechanical thinning in the surviving mixed conifer forests of the central Sierra. Choi is uncomfortable with simple translations from her science to policy. The forests, she says, are more various than the policy debates allow.

By midday the work is done. Choi packs her tablet into the truck. A red-tailed hawk circles above the burn. The wind picks up and carries the bear clover smell up the slope.

She thinks, sometimes, about what this place will look like in 2050. By then, the pines now at her shoulder will be twenty metres tall. The white firs, if they return, will be sparse and confined to the moister draws. The bear clover will have receded into the shade.

It will be a forest that someone, perhaps not her, will be paid to walk through and measure.

She locks the truck. The road back to Paradise is empty.