An Ice Age forest's last stand
On the upper slopes of Hallasan, a dormant volcano and South Korea's highest peak, lives a unique forest of Korean Firs (Abies koreana). This species, endemic to Korea, is a living relic of the last glacial period. As the ice sheets retreated and temperatures rose, these cold-adapted firs followed the climate they needed to higher elevations. The population on Hallasan became isolated, a pocket of subalpine forest now found mainly above 1,300 meters (4,265 feet). Today, this forest covers the largest single area for the species and is a site for understanding plant genetics and climate change.
The Korean Fir is classified as Endangered by the IUCN. Its habitat is shrinking due to rising temperatures, with some studies projecting an 80% to 95% decrease in thermally suitable areas with just a 2°C increase in temperature. The trees are sensitive to heat and drought stress, preferring cool, north-facing slopes and areas near streams. On Hallasan, the fir trees at 5,550 feet have a much lower survival rate than those just 550 feet lower, showing the direct impact of elevation and microclimate. This upward march for survival, with nowhere higher to go, is what scientists call the "escalator to extinction."
The genetics of survival
Scientists are studying the Hallasan fir population's genetics to understand its chances for survival. An analysis of the population using 10 microsatellite markers found moderate levels of genetic diversity. The expected heterozygosity (He), a measure of genetic variation, was 0.614 for the overall population. However, the population shows signs of isolation. Genetic differentiation between subpopulations on the mountain is low, with an FST value of just 0.041, meaning the different groves are still relatively connected genetically.
This genetic toolkit is what the firs will need to adapt to changing conditions. Researchers have identified that spring droughts are a particular threat. The firs have shallow, horizontal root systems that make them susceptible to both drought and being toppled by strong winds. Studies show that the population has been in decline since the 1980s. Conservation strategies now focus on using this genetic data to select the most diverse individuals for restoration projects, ensuring any new plantings have the maximum possible adaptability. Researchers have proposed an optimal sampling strategy of 35 individuals to capture the genetic diversity of the Hallasan population for such efforts.