Century-old Trees Help the Forest Grow

An interesting study from Canada’s McGill University recently indicated the particular value of old trees. In brief:

  1. Trees that are over 100 years old tend to have more moss growing on them at the 15-30 meter (i.e 50-100 feet) level or higher.
  2. These mosses provide a habitat for cyanobacteria.
  3. Cyanobacteria fertilize the forest by fixing nitrogen.

According to an article published in The Science Daily, researchers Dr Zoe Lindo and Jonathan Whiteley of  Mc Gill’s Department of Biology found cyanobacteria in moss growing high in the trees fixed twice as much nitrogen as those in moss on the ground.   Dr Lindo is quoted as saying: “These large old trees are doing something: they’re providing habitat for something that provides habitat for something else that’s fertilizing the forest. It’s like a domino effect; it’s indirect but without the first step, without the trees, none of it could happen.”

Of course, by providing this fertilizing effect and thus encouraging the growth of trees and other vegetation, it also helps to sequester carbon.


Most of the trees in Sutro Forest are over a century old, and many of them are 100- 200 feet high, and do have moss and epiphytes growing on them. This would suggest that something like this is indeed happening in the forest.

Of course, in Sutro Cloud Forest, the acacia subcanopy also helps to fix nitrogen. More than ever, we are seeing a beautiful networked ecosystem here, which is under threat of the removal of 90% of its trees, as well as much of its understory habitat.

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