[CANUFNET] Tree Growth Factors Question

Sat Oct 6 12:13:49 EDT 2018

In my experience there is no reliable rule of thumb for tree age vs diameter.  You can have two trees planted at the same time of the same species that have dramatically different DBH right beside each other, and this routinely happens with even-aged stands in the wild. If one is getting more sun and the other is suppressed there will be a large difference in diameter.

In a even aged stand, say red oaks, you can have one dominant tree in the middle of the grove that is taller and thicker than all the others growing around it.  The others may all be growing sideways to try to get to the sunlight as the centre tree spreads it’s crown out to capture all of the sun above them and are a lot different in diameter but all close to the same age.  In a conifer plantation in the early stages there can be a narrow range of sizes so easier to make age estimates from size, but as the plantation ages the dominant trees grow much larger than the suppressed ones, which die out eventually.

If you have some local data from core samples or counting rings of cut trees to compare with you could make up a rough table of age vs size that could be a fair estimate for each species most of the time.  It has to be local data – trees in Toronto or Niagara grow a lot faster than on the shield north of us.  You know that pines can be aged by counting the branch whorls eh?  There are also old MNRF publications that have age/height curves by species and site class that are based on good data and can be a good tool for estimating.

You hear people all the time describing 60cm+ trees as ‘100 year old trees’ that are often silver maples or willows that can’t be more than 60 years old since the area was developed then.

Stephen Smith
Urban Forester, ISA Certified Arborist
Qualified Tree Risk Assessor
Urban Forest Associates
www.ufora.ca
off 416-423-3387/cell 416-707-2164

From: Andrew Almas via CANUFNET 
Sent: Wednesday, October 03, 2018 1:23 PM
To: geospatialniagara at gmail.com ; canufnet at list.web.net 
Subject: Re: [CANUFNET] Tree Growth Factors Question

Hi Darren, 

There is no extra mathematical step to applying the growth factor. It is just that trees grow differently in different settings. So in the case of the growth factor provide by the Morton Arboretum they are only considering trees that are "landscape specimens", these tend to grow in diameter far more quickly than trees in a forest setting that tend to grow taller. Most growth factors you will find are associated with that species growing in a forest setting. That is the source of the discrepancy. Another source of discrepancy could be locale - a red maple in Quebec will grow more slowly than a red maple in Georgia...

Best,
         Andrew

On Wed, Oct 3, 2018 at 12:00 PM Darren Platakis via CANUFNET <canufnet at list.web.net> wrote:

  Hello everyone,  

  I was hoping to be enlightened with regards to tree growth factors and estimated tree age. I am not a arborist by trade so be gentle with me.

  I'm trying to apply growth factors to an inventory of trees to estimate age but some things do not make sense.

  By way of example, the growth factor for a Norway maple is noted as being 4.5 so in essence, a Norway maple with a diameter of 20 inches is estimated to be 90 yrs old - Diameter X Growth Factor (this number doesn't seem right to me). 

  However, there are several charts available that provide this information, such as one released by The Morton Arboretum that state a Norway maple of 20 inches in diameter is estimated to be 52 years old. This would be a growth factor of 2.6 (Estimated age / diameter = Growth Factor). My question is, why the big discrepancy? Am I missing a step somewhere?

  This is an exercise that I may like to take into a classroom but with the wide chasm of results I'd be wary of doing so. 

  Thanks in advance, 

  Darren Platakis
  BSC., GIS(PG), FRCGS

-- 

Andrew Almas
Lecturer
University of Toronto, Mississauga
Department of Geography and Programs in the Environment 
(647) 529-8867
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