DBH

[TeaW]

 'Northern Woodlands" had an article about diameter breast heigh.It stated that DBH is the diameter measured at 4.5 feet in the U.S., "metric DBH" is1.30 meters in Canada and Europe. I.2 meters in Japan and Korea -1.4 meters in New Zealand. Our local forestry by-law in central Ontario uses 1.37 meters(53.93 inches). It was an interesting article but I am wondering if 1.3 meters is the norm for Canada?

[solodan]

I don't know the answer to your question, but I have always wondered if you measure from the lowest grade elevation or the highest , or an average. ??? We have some very steep terrain here, and a large tree has a very different dbh if measuring from the downhill slope or the uphill.

[Ron Wenrich]

So, where does your stump start when you cut the tree?  Volume tables are built around taper and the first 17' log.  Measure from the high side and you won't have any problems.  Measure midslope or lowest point can throw in a bias similar to measuring below DBH.

[solodan]

Thanks Ron, that is where I would measure it from. Just did not know if that was where it was supposed to be measured from.

[Sprucegum]

Alberta and Sask. both use 1.3 m as DBH, taken at mid-slope or higher if you must, never on the lower slope.

[SwampDonkey]

Measured at 1.3 m on high side from point of germination. Some trees like yellow birch can have stilted roots. If measured high or low because of forking, swelling or safety then the difference in dbh is recorded (ie. measured low @ 0.6 m). Often on trees in precarious positions the point where you measured from will have a painted line. In BC, cruises are checked by MOF staff on occasion. Trees are also numbered and DBH lines drawn on the trees. Also, loose bark and moss are removed. A cruise point on the BC Coast can take 30 mins to an hour to measure and assess. Not economical to do here on the east coast and cruises are not often checked. I've seen some company cruises that I would call window cruising. In fact, I talked to a guy that admitted doing a few cruises from the pickup as an employee of a forest company.  : If the stand composition is one or two species than you might get away with it a few times. Had a landowner present two cruises to me one time. One was done by DNR and one from a consultant. The parcel was a piece of land being sold by the crown. Found out later the forest company that was managing this lot did the cruise and one of their staff was friends with the guy that did the second cruise. The peculiar part was, one fella was calling the maple (sugar maple) and the other feller was calling it (red maple) and the numbers for spruce and fir volumes were different but combined were the same volumes, and the whole volume cruise for the lot was exactly the same volume. Impossible if done independently, especially since I only seen two cruises of the lot. Coincidently, those two cases involved the same forestry company employee.  That company has been bankrupt since 1999. :

[WDH]

The purpose of measuring a log at DBH is to determine volume.  The convention is that there will be a 6" high stump.  So, to get the most accurate measure of volume, imagine that the tree will cut with a 6" stump from the closest point to the ground from the stump (the high side).

[Ron Scott]

On sloping ground the DBH measurement is taken from the uphill side.

[WDH]

When I said "high side", I was referring to the slope.  Brain and fingers don't always work in concert ;D.  Mr. Ron, thanks for my (pardon the french) fox pass.  (It is faux pas for our northern brethern to who english is a distant second and inferior language).

[SwampDonkey]

No worries WDH, 'high side' is the way it's written in a lot of cruising manuals.  ;D

[SwampDonkey]

For some reason I've found that some folks have been told to measure 1.3 m above the fork. Now that would be interesting if the fork was as 1.2 m off the ground and have to try the measure at 2.5 m. I think they didn't pay close attention in mensuration class.  ;)

[Ron Scott]

WDH, knew what you were saying. Just wanted to give the Dictionary of Forestry definition since the question was in regards to DBH measurements on a slope. ;)

[WDH]

Good.  Especially since we should not confuse the "slope-challenged" members of the Forum (now that is in no way intended to insult you "flatwood" boys and girls.  For the time being, the Boss is a "flatwoods" boy.  I am sure that Tom is showing him the "flatwood ropes)  8) 8) 8) 8).  DanG is "slope" challenged there in Chattohoochie, and I would never insult such a fine gentleman ;D.

[solodan]

Do they measure dbh from the top of the mud or the top of the water down in the swamp?  ;D

[WDH]

I guess we will have to ask the swampdonkey's and the swampgators and all the other denizens of the swamp that are on the Forum ;D.

[SwampDonkey]

Wait till the wet stuff crystallizes, easy peasy.  Or mark it NP (non-productive). ;D

[Ron Scott]

Ditto! These are "unsuited lands for timber production". We stay out of hydric soils and wetlands due to environmental concerns, equipment limitations, economics, etc. Best management practices are most difficult to perform in such ecosystems. ;)