The twisted, deformed shapes of very old pine trees may be a sign of an exceptional ability to adapt to stress that has helped them live for more than 600 years.
Ancient trees are important because they store large amounts of carbon, hold records of the past climate and serve as pillars of forest ecosystems. 鈥淟ike old people in human societies, they connect everything,鈥� says at the University of Barcelona in Spain.
Munn茅-Bosch and his colleagues went hunting for ancient trees in a forest of mountain pines (Pinus uncinata) in Alt Pirineu Natural Park in Catalonia, Spain, combing a section of 1300 trees at high altitude that was exposed to cold, harsh weather. They chose this area since stressful conditions tend to produce the oldest trees because they have to slow their growth to cope, which ultimately extends their lifespans.
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Most of the trees in the forest were around 200 years old, but the researchers found 12 ancient trees aged approximately 660 to 750 years old. They identified these rare individuals by looking for trees with trunk diameters exceeding 1 metre and estimated their ages based on the known growth rates of mountain pines.
The team noted that the 12 ancient trees shared a number of striking characteristics. Most pine trees have a main central trunk that grows more strongly than its side branches 鈥� a trait called apical dominance 鈥� but all the ancient trees had thick side branches that competed in size with the central trunk.
These side branches often took unusual, twisted forms, suggesting these trees had a high ability to adapt to changes in the environment, known as plasticity, says Munn茅-Bosch.
Another common feature was 鈥渕odular senescence鈥�, meaning that large sections of the trees were dead while the rest continued to thrive and sprout new shoots. This is another sign of plasticity, since it suggests that ancient trees can survive damage by sealing off the injured parts, says Munn茅-Bosch.
The oldest known living tree is a (Pinus longaeva) in California called Methuselah, which is about 4850 years old. It also lives in cold, harsh conditions and has twisted branches, large dead sections and loss of apical dominance.
At this stage, it is unclear whether the unusual plasticity observed in ancient pines is a result of their age, or whether they had higher plasticity to begin with that allowed them to reach very old ages.
鈥淚t鈥檚 quite difficult because the only way to answer this question would be to study individual trees over their entire lifetimes, which are hundreds of years,鈥� says Munn茅-Bosch.
Nevertheless, now that we know how to spot ancient pine trees, it should be easier to find and protect these precious individuals, he says. In the past, 鈥渋t has been a problem for the scientific community to identify these really ancient trees鈥�, he says.
His team plans to study other tree species to find out if individuals that reach very old ages display the same unusual features as ancient pines.
Although some trees can live to staggeringly old ages, they won鈥檛 live forever, says Munn茅-Bosch. Even if they can escape human logging, they are likely to succumb to a lightning strike, wildfire, storm or other large stressor that will overwhelm their survival mechanisms, he says.
Plant Physiology
