Managing veteran tree management

The management of ancient and veteran trees has become very topical and this is not necessarily a bad thing.  Managing venerable old trees requires a different mind-set, and I quite like that.  Sometimes it’s best to throw the rule book away, do something drastic or sometimes it’s best to do nothing at all.

But before we can consider saving something old, we need to know why it dies; why it dies, not how it dies.

We humans die of old age – assuming we get the chance that is.  The how differs but the commonality is that our chromosomes lose the ability to accurately replicate themselves.  As we age the copies start to get a bit faded and eventually, so do we.  Trees don’t have that issue, trees don’t die of old age.  Trees can accurately replicate their cells for as long as they can get water and nutrients to where the copies are being made [the meristems].  In theory, trees could live forever; but in reality, they don’t.  So why do trees die?

One of the many theories is that trees die because they get to a point where they no longer have enough photosynthetic resources to support all their ‘dead’ tissue.  As theories go, this one doesn’t seem to make sense; why would a tree invest resources on dead tissue?  Trees wouldn’t; they are not emotional, they don’t think and they wouldn’t invest resources on dead tissue – unless that tissue wasn’t actually dead!  So, we should re-word that theory to ‘trees die because they get to a point where they no longer have enough photosynthetic resources to support all their ‘un-dead’ tissue’.

So, what is all of this un-dead tissue? When most of us think of wood, we are thinking about the plant tissue called xylem.  In older trees, most of the tree’s xylem is heartwood, and we’ve been taught since ancient trees were young that heartwood is dead.  Technically, depending on which definition you choose heartwood is dead, the nucleus of the cell has stopped beating, its dead.  But there is still quite a bit going on in and around these dead cells, so much so that to call them dead is a bit on an overstatement; its more un-dead, than dead.

The heartwood is dead, long live the heartwood…

In real terms, what does this means and what has it got to do with the management of ancient and veteran trees?

When a tree gets to a point where it has too much bulk, too much tissue to maintain with the resources that it has available it must shut down and/or shed some of that bulk.  In the natural environment, some trees will retrench; they will retreat in on themselves.  They will stop supporting some of that un-dead tissue, let it fall away and channel water and nutrients where they are getting better return on their investment. Google the ‘Arthur Clough Oak’ and you will see 100 years of this in action.

We need to keep this process in mind when we consider managing veteran trees; in fact, we need to keep this process in mind when we manage all our trees, if we ever want any of our trees ever to become veteran trees.  For a tree to retrench or retreat in on itself, it needs to have somewhere to go back to – if we keep thinning our trees, and removing all the epicormic growth, then we reduce the options available to the tree.  Much of our current management practices could well shorten the life of our trees.

So how to manage veteran trees?  There isn’t a rule book when comes to veteran tree management, although the UK’s David Lonsdale and the Ancient Tree Forum do have some fantastic resources.  The key point (which the ATF make several times) is that every tree needs to be considered as an individual; each tree, its position, condition and importance needs to be considered.  And then whatever you do (or don’t do) needs the investment of time.  If you have a structure that could live forever then you need to adjust your time scale; five, ten, fifteen years maybe.  If you are going to do it, then commit to it for the long term and know that if done well it could out live you and many generations to come.