- August 24, 2016 - Jardin botanique : Secrets of plants
What age do trees die at? That’s a difficult and intriguing question.
What does a 100-year-old oak tree look like? Is it so different from another individual that may have reached 400? If the first one grew in ideal conditions and the second, on the other hand, suffered from a lack of water or sunshine, it’s possible that the two will have reached a similar size. Some species demonstrate particular growth strategies. For example, the beech tree can slow its growth until a neighboring tree falls and creates a light gap that it can benefit from. At that point its pace of growth will accelerate significantly. In these circumstances, it’s impossible to determine age on the basis of size.
We know that some species of tree can live for hundreds of years. That’s the case with certain oaks, firs, larches, pines, beeches, elms, and others as well. But there are even some English oaks that live for 2,000 years! Transposing that situation to human beings is inconceivable: relatively speaking, it would mean certain humans would live to 250. With trees, there’s nothing to keep them from breaking such records. And in fact, scientists have determined that trees are not programmed to die like other living beings. How is that possible? We first have to ask the question, what is it that gives rise to old age. In animals, genes stop working through a biochemical process called methylation. This degradation of the cells, combined with other factors (old age is a highly complex phenomenon), causes wear and tear on vital functions and eventually shutdown. In other words, old age is due to the accumulation of genes that go out like so many candles.
Could it be this link to the changing of the seasons – tropical trees slow their growth at certain times of the year – that allows trees to escape the degradation of cells? Nevertheless, trees do die – that much can’t be doubted – but they’re rarely carried off by old age. Their end is often brought about by external factors: fire, lightning, a saw… If time is on their side, they’ll die a piece at a time, slowly. They’ll lose their thick branches, stretch out less and less every year, become more vulnerable to disease. That process may last hundreds of years, until one spring the sap no longer rises: the tree is dead. But it’s impossible to determine in advance when that end will come.