Old Trees are Key to Preserving Mountain Forests

Jenn Hoskins
6th February, 2024

Old Trees are Key to Preserving Mountain Forests
Image Source: © Natural Science News. This image is an artistic rendition.
Ancient trees are increasingly rare, particularly in Europe’s mountainous regions, and their importance to the surrounding ecosystem is only recently being fully understood. These trees aren’t simply old versions of younger trees; they possess unique characteristics that make them vital for biodiversity. A new study from the University of Barcelona[1] investigates how these exceptionally long-lived trees contribute to the biodiversity of mature forests, specifically focusing on the traits that allow them to survive for centuries and their role as habitats for other species. The research centers on Pinus uncinata, a mountain pine species, and examines trees ranging in age from young to ancient – some exceeding 700 years old. The core question the study addresses is whether these ancient trees function as crucial “biodiversity anchors,” supporting species that struggle to thrive elsewhere. The study found that while older trees inevitably face age-related limitations in growth, they exhibit remarkable physiological adaptations. These include a loss of strong apical dominance (meaning the main stem doesn’t completely suppress side branches), the ability to grow new shoots from beneath the bark (epicormic growth), and a modular approach to senescence – where parts of the tree can die off without jeopardizing the whole organism. Crucially, these ancient trees demonstrate a significant plasticity in their tissues, allowing them to adjust to changing conditions. This physiological flexibility isn’t just about survival; it directly impacts biodiversity. The researchers observed that ancient trees provide a unique habitat for certain species, particularly vulnerable lichens like Letharia vulpina. Lichens are symbiotic organisms – a partnership between a fungus and an algae – and are sensitive indicators of environmental health. The study suggests that the specific conditions created by these ancient trees are essential for the survival of these lichen species. Interestingly, this research builds upon earlier work that explored the evolutionary history of pine trees[2]. That study revealed that most pine species diversified relatively recently, during the Miocene epoch, and that mid-latitude regions acted as “evolutionary museums” preserving older lineages. This suggests that the ancient trees studied in the current research aren’t simply survivors of a bygone era, but represent a continuing legacy of evolutionary adaptation within the pine family. The findings also connect to research examining the impact of non-native tree species on lichen communities[3]. While that study found that introduced pines could support similar lichen richness to native species, it highlighted differences in composition – the specific types of lichens present. The current study suggests that ancient trees, with their unique physiological traits, foster a distinct lichen community that might not be replicated by younger or non-native trees. The differing canopy closure and habitat availability between tree species, as noted in the earlier lichen study, likely contribute to these variations. The Barcelona team’s research emphasizes that the size and age of a tree directly influence its growth rate, bud development, and water management. Ancient trees, despite their slower overall growth, possess a resilient metabolism and a capacity for “modular autonomy” – the ability to function effectively even with localized damage or loss of parts. These traits allow them to maintain their role as biodiversity hotspots. The study’s conclusion is that the longevity of these trees isn’t just a matter of surviving for a long time; it’s about accumulating a unique set of evolutionary tools that drive specific ecological relationships. These relationships, particularly those with vulnerable species like Letharia vulpina, are irreplaceable and essential for the health and stability of the entire ecosystem. The physiological traits developed over centuries or millennia are key to this function.

EnvironmentEcologyPlant Science

References

Main Study

1) Ancient trees are essential elements for high-mountain forest conservation: Linking the longevity of trees to their ecological function.

Published 5th February, 2024

https://doi.org/10.1073/pnas.2317866121

Related Studies

2) Phylogenomic and ecological analyses reveal the spatiotemporal evolution of global pines.

https://doi.org/10.1073/pnas.2022302118

3) A Pine Is a Pine and a Spruce Is a Spruce--The Effect of Tree Species and Stand Age on Epiphytic Lichen Communities.

https://doi.org/10.1371/journal.pone.0147004


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