Friday, May 8, 2009

The Afterlife of Trees




I think it might have been Oliver Rackham, botanist and noted expert on woodlands, who once commented that the only object in woodlands more valuable than a live tree was a dead one, since they host so many species of wood-boring beetles and other insects that breed in dead wood. This ancient beech stump, in Durham University Botanic Garden’s new woodland nature trail, is riddled with emergence holes from insects that have bred in it, but its most conspicuous features are the magnificent specimens of the bracket fungus (Ganoderma sp.) that was almost certainly the cause of its death. This parasitic fungus weakens the tree and infected trunks typically snap somewhere above head height during gales. The fungus is perennial, so each year the bracket develops a new zone of spore-producing tissue around its periphery and generates so many spores that they cover the vegetation below with what looks like a layer of cocoa powder. You can estimate the age of the bracket by counting the number of ‘steps’ on its upper surface; each marks the end of a year’s growth. During their ten years of existence, these brackets must have produced billions of spores. You can read more about the woodland nature trail at http://www.dur.ac.uk/botanic.garden/?itemno=7173


3 comments:

  1. I am always surprised how long a dead tree trunk survives. I have the remains of a corkscrew willow that I had cut down as it grew too tall too fast. The stump is about six foot high and it must be over fifteen years since it was lopped but it still stands firm. Like the beech stump there this one is riddled with holes and the bark is peeling off but no fungus seems to have taken to it.

    ReplyDelete
  2. That bracket fungus certainly has a beauty of its own. I love that first shot.

    ReplyDelete
  3. Thanks for your comments, Midmarsh John and Holdingmoments. There seems to be an interesting variety of insects that live in the fungus, as well as the dead wood. Some of these long-lived bracket fungi have an amazing range of insects that breed in them. I once kept an old razor-strop fungus bracket in a sealed jar to see what would emerge and a whole series of flies and tiny beetles hatched. I've got several decrepit stumps in my garden, cut off at about four feet above ground level, from trees that grew too fast too quickly. I originally intended to dig them out but never got around to it, and last winter a great spotted woodpecker visiting them.

    ReplyDelete