Tree's "Landscape" Life Expectancy ?

mdvaden

mdvaden

Participating member
Location
Beaverton. Oregon
Tree\'s \"Landscape\" Life Expectancy ?

Any of you encountering more of the term "Landscape life expectancy of a tree"?

When I attended tree ID course at the local college in the 1980s, we used to get the mature size or potential size of species.

When repeating a deciduous tree class not long ago, every species was accompanied by a "landscape life" too.

After doing this work now for decades, I'm beginning to see that maybe less than half the trees around here were planted to exceed "landscape life expectancy".
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

I didn't have time to read your article till after work. Maybe you mentioned this but how about this theory. That any species of tree has potential to live forever but something always causes their downfall. I suppose the same is true of anything alive even us.
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

In the college class I repeated, the basis for landscape life of each species was not really explained. Whether its due to an average of reaching damage causing proportions, or exceeding an average homeowner's expectations.

It seems that there could be a clash over this kind of thing. Because some people or committees are dedicated to preserving trees as long as the plant can survive. But other folks, if they approach planting from "landscape life expectancy", may plant with the intentions of replenishing at decade intervals?

There has been some head-butting over this type of thing for many years already. But if colleges, and other, are now increasing education about prescribed life expectancy, could conflicts get better or worse?
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

I think KT Smith's excellent articles point out it's all about context, where the trees are. Urban and landscape trees face unique threats in regard to root zone disturbance from development, vehicle impact injuries, soil compaction, lack of duff layer etc. Any given tree species can be described in terms of average life span in an optimal setting, once the tree is in the "human made" landscape all bets are off. Preservation of marginal landscape trees is often related to a landowner or general public's (in public parks) desire to keep a notable or favorite tree going beyond what the tree can actually can sustain in the context.

Looking at it that way I think a tree species average life expectancy can only be a general guideline, where the tree is located will be the determiner.
-moss
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

Thanks Moss for the kind words!

A key concept from modern biology (since Watson and Crick, let's say) is that of programmed cell death or apotopsis in multicellular organisms. There's a quick Nobel prize for anyone to come out with a unifying explanation good for all organisms, but the gist of it is that individual parts seem to have a certain service life. Maybe it's in units of time, maybe it's in the numbers of takeoffs and landings (as with aircraft), maybe it's in the number of serial mitoses (sort of like multi-generational copies of audio tapes). And there is individual variation, certainly from species to species and from individual to individual.

Although the replication systems are really good, say of cambial cell divisions through the life of the tree, errors may creep into the DNA or the telomeres (the ends of chromosomes that are like points of attachments for the replication machinery) marking the number of divisions. Once you get at the end of the rope, so to speak, the systems break down. The "telomere effect" was the explanation when I was in school 30 years ago, and I'm sure there are more modern and maybe better explanations, but most research biologists (like me) figure apotopsis is the normative state. I think of cancer diseases as the loss of functional apotopsis, the cells just keep on dividing.

I'm not claiming infallibility here, this is just a pretty-well accepted concept. Smarter people than me work on this!
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

When doing landscape designs, it was explained to me the plants chosen had a definite service life within the landscape design with respect to the maturity of the plants. The design did not have an indefinite service life. So, to plant a tree with a specific service life in mind is not unacceptable. The choice of location, longevity, and function of the plants belonged to the clients and landscape designers.

Joe
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

The concept of "landscape" life expectancy also makes landscape planning a lot easier. For instance, one could argue that Bur Oak makes a great street tree. Looking at it's landscape life expectancy, (disregarding the even shorter life span of urban street trees), a bur oak would fit well along a road. Not so the 200 yr. + monster that graces our college campus. But do you need to account for maximum potential size?

I can remember one of my first landscape design classes, and drawing a circle for a tree at it's full size, according to Dirr, and wondering what I was going to do with the rest of the yard, cause the tree circle just took up the whole piece of paper.

What I dislike about this concept is the marketing reek I think I'm smelling nearby. (and no, it's not me, I showered after work) Does landscape life expectancy imply some "replacement schedule"? Can you sell more woody plants by implying your tree has reached its landscape life expectancy?

Then again, I'm cutting down some over-mature trees around a house being restored in a couple of weeks as they are evergreens that are no longer providing the screening from the busy road they were intended to block.

Does landscape life expectancy get a poor designer or planner off the hook for picking the wrong tree in the wrong place? A swamp maple will have a shorter life expectancy planted in a sandbank, but when it up and croaks you can just say it reached it's L.L. Expectancy in that location. Go ahead and plant whatever you want wherever, all trees have a life expectancy, so don't worry too much about the long term.

Tim, busy confusing himself.
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

old concept--see SULE by jeremy barrell, which has now morphed into a Tree A-Z system.

also see peter del tredici and neville fay etc on tree immortality

i don't like using those kind of numbers or even prognoses--too many variables, not least of which is client goals. most of my clients want the tree preserved in any reasonably useful form. and yes the numbers enable copouts for screwups.

what is their purpose again?

o and kevin it's not clear in the caption in the 2nd piece--how does compartmentalization add to risk--izzat a typo?
mad.gif
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

Thanks Guy,

My point on that caption, and maybe it's wrong-headed, is that compartmentalization can contribute to a tree surviving and being upright after (sometimes long after) there is substantial risk of catastrophic failure. I think that is a real tradeoff. Not for the tree, even with risk of failure, every day is a bonus day, but for the built landscape. No, I'm not against compartmentalization! That would be too ridiculous. It's just a tradeoff.
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

Ohhhh ok i see the tradeoff, and the caption referred to the negative aspect re the built part.

substantial risk of catastrophic failure...that would seem to change a great deal, depending on what tissue is added and what tissue is removed. not a static condition by any means. pruning and support reduces risk, and in terms of wall 4 so does codit right?

so substantial could slide down to "slight", and catastrophic to serious, for instance.

but the article, and this thread, look not a the tree per se but seem to focus on its context. so i understand the caption a little better now.
 
Re: Tree\'s \"Landscape\" Life Expectancy ?

[ QUOTE ]
... most of my clients want the tree preserved in any reasonably useful form. and yes the numbers enable copouts for screwups.

...

[/ QUOTE ]

One thing that came to mind the day after posting this topic, were tree toppers.

Wonder if an established standard for "landscape" life expectancy could leave an open door for toppers to escape responsibility.

Like suppose 40 years was landscape life expectancy on a 90 x 90 lot for, say, an Acer rubrum or something. So a tree topper figures that if trees are over 40 years old nobody can complain about them.

Or in the case of Portland that has an ordinance against topping, then they might have a legal loop-hole to dodge consequences.

?

cool.gif
 
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