Ways to estimate a tree species' DBH at a certain age

[BotanyGem]

Hi everyone, I am doing a student research project for my degree and came across this forum which pointed me in the direction of some very useful Forestry Commission PDFs (thank you!).

 

I just wanted to ask a quick question as you all seem so knowledgeable!

 

Is there an easy way to estimate a tree species' diameter at breast height at a certain age?  I would like to be able to create a list of different tree species and say (on average) what their DBH would be when they are 30 years old.

 

E.g.

 

Average English Oak at 30 years = 100 cm DBH

Average Wych Elm at 30 years = 70 cm DBH

 

Etc.

 

Could anyone suggest a way to do this please?  Ideally I would like to make a list of several UK tree species and estimate their DBH when they are 30 years old.

 

Thanks in advance for your help!  I feel like I’m going around in circles trying to find the info online.  I've seen the Forest Yield software programme which looks like it might do what I need it to do but it costs £50 + VAT.

 

 

[Chris at eden]

Are you doing forestry or Arb?

[Tommy_B]

Welcome to the forum! I'm guessing you would want it as forest ground specimen? What is the purpose of collecting the data?

[drinksloe]

Will it not change so much from area to area, even locally due to soil and soil conditions, drainage, exposure etc, never mind other management styles thinning, planting distances.

 

A site we just finished the trees onset side m off been 10-20m shorter and tiny ( the smallest trees only good for sticking under tracks) compared to the quite decent trees on East side of that wood.

And that was only sitka at around 25 off years

[trigger_andy]

39 minutes ago, drinksloe said:

Will it not change so much from area to area,

I guess that was not meant? 

[daltontrees]

Have a look for the Forestry Commission publication by John Whyte, it gives annual growth increments for several species in a variety of growing conditions. It gets complicated as trees get older, but initially it's just a simple multiplication. If you can't find it let me know.

[Paul Cleaver]

3 hours ago, daltontrees said:

Have a look for the Forestry Commission publication by John Whyte, it gives annual growth increments for several species in a variety of growing conditions. It gets complicated as trees get older, but initially it's just a simple multiplication. If you can't find it let me know.

Does it take into account trees in a woodland setting?  As we know increment will be lower for trees in such a setting.  

[daltontrees]

I'll check the wording, as I've only ever used it for individual open grown trees.

 

For forestry trees there is a massive database at Forestry Scotland for just about every species of forestry tree in every possible permutation of soil types and climate. I wsa gobsmacked when I found it. It even has a sort of calculator where you put in species, location, slope, soil type etc and it gives you stand yield info which with a bit of jiggery pokery can give average individual tree sizes.

[BotanyGem]

Hi everyone, thanks very much for getting back to me!  The purpose of the research is to estimate how much carbon different tree species would store over 30 years from being planted as small whips.  If I know their DBH at 30 years I can use this to calculate the carbon they have (theoretically) stored and then see which tree species stored the most and least.  I realise this will depend a lot on location, soil, site etc, but it was just an average DBH that I needed.  It's for an environmental science project assignment, from the angle of carbon sequestration for climate change purposes.

 

Thanks for suggesting the Forestry Commission publication by John Whyte, I'll take a look at it.  It's great the FC have so many books available as free PDFs, some very interesting reading. 

 

I'll have a look at the Forestry Scotland database too - that sounds interesting!

 

Someone else has also suggested the yield tables used in the Forest Yield software so I can hopefully get hold of these and work it out manually without spending £50 🙂

 

Thanks again for your help!

Edited February 27, 2021 by BotanyGem
Updated response

[daltontrees]

Carbon is stored mainly as cellulose, lignin and less permanently as starch. So, dried wood density is a rough measure of carbon storage. Density is a product of growing conditions and species. It might not be a simple as carbon is proportional to cross sectional area. There might be an adjustment to be made from overbark DBH to overwood diameter.

It sounds like yield figures might be more useful too, becasue they will indicate biomass. Forced dense forestry produces tall poles with little side growth, and these may have the same DBH as an open grown tree of half the height and less biomass.