How do I figure trunk size from tree canopy?

[eepjr24]

So I know before I even type this that likely few people are going to go to this level of detail, but I like things to be in the right ballpark of correct in my drawings and for that I need a range. So if I have a canopy of a tree and I want to know how big the stump would appear, what is the answer?

I am going to provide my simple answer here for future reference, but if we happen to have an arborist who can provide better numbers (or heck, even an experienced gardener) please feel free to respond and supplement or disprove my figures.

Notes: I used the dbh method for calculating diameter (diameter at breast height). A quick google search will let you replicate if you like.

I measured an orange tree in my yard. Trunk diameter is approximately 12 inches (30.5 cm), canopy is approximately 18 feet (550 cm), giving a ratio of 1:18. Stated another way, the trunk is about 1/18th of the width of the largest canopy diameter.

Next, I measured an old oak tree in my yard. Trunk diameter is approximately 24.2 inches (61.5 cm), canopy is approximately 60 feet (1829 cm), giving a ratio of 1:30. Stated another way, the trunk is about 1/30th of the width of the largest canopy diameter.

I picked these two because they seemed representative of a reasonable range for canopy to trunk diameter. The cedars in my yard would probably yield a better number for coniferous trees, but I am assuming deciduous at the moment.

So, my answer for now is between 1:18 and 1:30 is reasonable.

- E

[Azélor]

One thing to consider is whether the tree is in a forest or solitary.
Trees in the forest are very tall and narrower than the ones in you backyard because they are competing with the other trees around them.

Is it a top-down or isometric map ?

[eepjr24]

Top down. And the oak in my yard is quite in competition, it is surrounded by other oaks and limited somewhat by the canopy of a very large (25m+ tall) pecan tree. The orange tree, not so much.

- E

[Gamerprinter]

Trees don't have a consistent ratio between trunk diameter and the canopy - leaf and branch distribution and how wide or how tall it is completely depends on which species of tree your talking about. There is no basic ratio that all trees follow. Some trees like Baobab trees have huge diameter trunks compared to the canopy. Some trees like those in Madigascar have a wide by flat (table-like) canopy over a skinny trunk. So there's no rule you can follow - it's all sort of generalizations and guesswork.

[eepjr24]

I gathered that it was not exact. But if I know the type of tree I am working with (live oaks, for example) and the trees have 20m canopies, the trunks won't be 2m across and they won't be 20cm across. Maybe I should start a chart by species, which honestly was what I expected to find on the web. And I found a couple specific locales (research papers mostly) but they did not always get very specific with the trees. And I know for the US that the Forestry service has this kind of ballpark information by species for dbh, canopy, height, critical root zone, etc. It gets used in aerial photo forestry growth and health analysis. I just have not been able to locate the documents if they are online (which who knows, they may not be).

The information you cite was kind of what I am looking for. If I want a species of tree with huge trunks that are subtropical... what will the canopy be in relation to that trunk?

- E

[Redrobes]

Trees don't have a consistent ratio between trunk diameter and the canopy - leaf and branch distribution and how wide or how tall it is completely depends on which species of tree your talking about. There is no basic ratio that all trees follow. Some trees like Baobab trees have huge diameter trunks compared to the canopy. Some trees like those in Madigascar have a wide by flat (table-like) canopy over a skinny trunk. So there's no rule you can follow - it's all sort of generalizations and guesswork.

I think that is very true - but it might still be quite useful to have some kind of guide range for a selection of common species.

(got ninja'd there - but yes... that !)

EDIT #2: This site has a great chart for some common species...
https://gabrielhemery.com/estimating-tree-crown-size/

[eepjr24]

Awesome!

I found one more for 4 species in the Minnesota / Nebraska area.

http://www.notesontrees.com/crown-di...alculator.html

[waldronate]

An additional point is that most charts will be for "reasonable" trees. Due to the square-cube law, things get disproportionally thicker as they get taller. Tropical trees are likely to change shape as they approach their size limits (buttressed trunks are common in large trees in questionable soils). Another common tropical form factor is multiple support trunks for like banyans and mangroves.

A fun search to get the visual impact is "tree shapes identification" on Google images. You'll get silhouettes that give you a quick overview of the wide diversity of shape in the crowns of trees.

[eepjr24]

Okay, I found an excellent source for many different trees but it will require some math for each given species. However, it lists a large amount of good data. =)

https://www.portlandoregon.gov/parks...le/433143#data

Scroll to the bottom and you can get the tree inventory of the Portland Oregon Park System. Over 300 tree types, 25,000 living trees.

- E

[Kier]

Okay, I found an excellent source for many different trees but it will require some math for each given species. However, it lists a large amount of good data. =)

https://www.portlandoregon.gov/parks...le/433143#data

Scroll to the bottom and you can get the tree inventory of the Portland Oregon Park System. Over 300 tree types, 25,000 living trees.

- E

Oh wow, that is awesome, click on the tree and it gives you the info. I didnt realize crowns can get that big, had read somewhere 35 feet was normal. The first 1 I saw was 52 feet.