The oldest, knotted, scarred pine tree on Earth is a boon for forest life.
Researchers published a report in the Proceedings of the National Academy of Sciences on Feb. 5 that these ancient mountain pines (Pinus spp.) provide food and shelter for lichens and insects, not only because they are old, but also because of what made them grow so old in the first place. These findings highlight the broader importance of tall old trees and suggest that development, fires, or threats to their survival from climate change can cause irreparable harm to some ecosystems.
Old trees continue to decline around the world (No. 6 18 18). In Europe, the few remaining forests with a large number of old trees represent only 07% (or just under 3.5 million acres). Joseph Birch, an ecologist at Michigan State University in East Lansing, who was not involved in the study, said that this and others like it are "really good because they show how important ancient growth is." This work reminds us that we need to take a long-term view of old trees. "We need to manage and protect the forests we have now, even if they're younger, so that our descendants can have more ancient growth in the landscape in hundreds or even millennia," Birch said. ”。
Ancient and knotty mountain pines.
The ancient mountain pine has grown over hundreds of years and has grown twisted and curved. As shown by this tree in the Aigüestortes i Estany de Sant Maurici National Park in Catalonia, the dead and decaying part of the plant can serve as a habitat for several forest species.
While plant physiologist Sergi Munné-Bosch and ecophysiologist Ot Pasques at the University of Barcelona are interested in the aging of pine trees, which may be hundreds of years old, they are also curious about how senescence and tree decay affect the wider forest ecosystem, with different stages of life and decay providing different habitat needs for plants, animals, and lichen species.
Previous studies have tended to look at how individual trees age. Therefore, Munné-Bosch and Pasques decided to upped the ante. They studied young, adult, and extremely old mountain pines in five different regions of the Spanish Pyrenees. The two calculated the age of the tree based on the circumference of the trunk. (These two traits are related, and there is no need to take a sample from the trunk to count the rings). The team also weighed and measured needles, buds, and buds, analyzed biochemicals in tree tissues that were involved in stress, decay, and growth, and noted age-related physical features in the trees, such as bare root systems, cracked bark, and lightning scars. Data on other species living on or on trees are also recorded.
The results showed that the oldest trees no longer put a lot of effort into propagation, reducing the production of cones and buds, greatly slowing their growth, and prioritizing stress tolerance and long-term durability. Ancient trees also allow parts of their bodies to die and decay along with the living. These are all adaptations to survive for hundreds of years, leaving the oldest trees knotted, scarred, and filled with large swaths of dead parts that are used by other forest organisms.
Ant colonies and plants like mountain leeks (sempervivum montanum) live in these dead and decaying areas. Trees with biochemical changes associated with decline and decay also tend to contain more lichens, while larger, older trees have a higher diversity of lichens. "Lichens look for very special micro-habitats in the mountains to survive," says Munné-Bosch. ”。For example, wolf lichen (Letharia vulpina) is rare in this part of Europe, and when the team came across it, it grew mainly on ancient pine trees.
Lichen on the old mountain pine.
In the Alt-Pirineu Natural Park, high in the Spanish Pyrenees, lichens grow on the knobby branches of an ancient mountain pine.
Young pine trees do not have the physical and physiological characteristics that are characteristic of ancient trees and cannot support forest life in the same way that ancient trees do. This makes the ecological role of ancient trees "irreplaceable", says Munné-Bosch.
"For many people who work on old trees, this is something we know intuitively," Birch said. But it doesn't have to be presented in this way, and there isn't necessarily such convincing evidence to back it up. ”。
He noted that these results are only applicable to a single tree species. In giant redwoods that have lived for thousands of years, senescence does not cause the shape of the trees to distort dramatically as stunted mountain pines that grow at high altitudes, so the impact of ancient redwoods on biodiversity may vary.
Munné-Bosch says the team's next step is to conduct research on other tree species.