It’s common to see trunks of ancient trees draped in a colourful carpet of moss and other primitive plant growth. These mosses, lichens and liverworts are non-flowering plants whose ancestors can be traced back to long before the dinosaurs walked the earth and now, in the 21st century, one of the most common places to find them is on the bark of our old trees. These ancient plants are the subject of this week’s blog.
I know this sounds a little dull but bear with me.
Mosses evolved 470 million years ago and were the first plants to move from the ocean to the land and were responsible for changing our atmosphere so that animals from the oceans could also come ashore. As larger and more advanced plant species evolved the rocky habitat that mosses needed often became too competitive to survive and one of the natural surfaces they moved to was the bark of the very trees that had taken over their home. Any single tree can have dozens of species of moss on it and in some cases the moss can form a layer so thick that it becomes vital to the tree as insulation and protection against direct sunlight.
Liverworts are one step up the evolutionary ladder from mosses – a little more advanced but still pretty basic. They love damp shaded places and the base of many trees among the leaf litter is often perfect.
Now lichens are not just plants they are also fungi – lichens are organisms made up of both plant cells and fungal cells that live together, work together and reproduce together. They share everything from space, to nutrients. These organisms are very sensitive to pollution and to this day nobody has developed any kind of device that can detect as minute an amount of air pollution as lichens can indicate. Therefore where we can see a wide diversity of lichens we know that the air is very clean. As with everything at this scale the lichens support a mind boggling array of specialist invertibrates.
Because many of these primitive plants are so slow growing they can only be found in large numbers on very old trees and so it is massively important to protect everything that grows on a veteran tree.
Tree Trivia: Historically ships were made of wooden beams and were usually oak. In order to give a ship the correct shape the beams need to be curved and in order to get the ideal shape foresters would hang weights or tie ropes to young branches to cause them to grow curved. This is of course where the word for a ships “bow” comes from.