?? about timber valuation

[sprucebunny]

Is there a difference between a timber cruise and a timber inventory ???

[Southside]

I imagine a timber cruise would not be nearly as much fun as say a Singles Cruise, a Bahama or Alaska cruise. Plus I suspect the ship would get stuck a lot in the pines.  :D

[sprucebunny]

 :D

Think I'd like the timber cruise better. I'll just take a small boat and get to skip the tourists

After further reading, I guess they are the same thing.

[WDH]

Yes they are essentially the same.  A timber cruise is a systematic random sample to determine the volume and type of timber which is essentially an inventory of timber volume and timber type. 

The level of accuracy is important.  If you are buying the timber off of the cruise, it is important that enough sample plots are taken to ensure the level of confidence.   If the cruise is to determine inventory for management purposes, a less intense cruise may be good enough. 

[Southside]

I used to get those calls telling me I won a free cruise.   ;D

[BaldBob]

Is there a difference between a timber cruise and a timber inventory ???

To be technical the difference is strictly that a timber cruise is the process of determining the inventory. Cruise = process. Inventory = result of cruise.

[SwampDonkey]

And most cruises would have stand typing if there are distinct groups of trees, but of significant area, say 8 acres of cedar in one and 20 acres of sugar maple in another. And there may be for than one cedar stand etc... on the property as well.

[sprucebunny]

Thanks for the replies.

Does the prism size affect accuracy or just the size of the trees sampled ?

I read this article which explained quite a lot.
https://apps.dtic.mil/sti/pdfs/ADA299918.pdf

[SwampDonkey]

The prism used affects plot size, it's not a fixed area, only a fixed prism angle. If the prism angle is such that you don't capture enough sample trees per point then it can affect accuracy to a degree. If you're in smaller wood and trees are 6-8", and the stand density (spacing) is not tight, you might pick up 4 trees in a smaller capture area, whereas the same prism in big wood with closed canopy might pick up 14 trees and cover a larger capture area. I consider 8 trees per point to me a minimum. I remember on the west coast, we often used 3 different prisms, one would be chosen for the harvest area, but a couple of samples would tell us if we were capturing enough trees. We could be on a block with 20" wood, another block might have 60"+ wood. If we used the prism for the smaller wood in the 60" stuff, we would have way more trees than needed and cost per point would go up. Typically in the north east we use one prism around BAF of 8-10 ft²/acre or 2 m²/ha. If your in a lot of 20-40" wood, than a BAF 40 ft²/acre or 9 m²/ha might be better. Typically, you get one or two big diameter trees in that class and a lot of smaller ones. But if your average runs 30"+ dbh in closed canopy, a 40 ft²/acre will capture 8 or more trees. That's very rare in the east, your looking at managed large white pine or red spruce stands.

[sprucebunny]

Are there standards for the density of the sample plots that are determined by the level of detail desired ? For instance; selling the land to an entity that has interest in the timber. 

[SwampDonkey]

I think it is rare to see any cruising standards handbook in the east unless it is internal with the forest service or state or mill with large land holdings. Otherwise, I think most are written for west coast species in Washington State or British Columbia. British Columbia has an accreditation board.

I think as far as the timber inventory, it is up to both buyer and seller to do their due diligence.

[WDH]

In most cases when buying timber, my Company did a 10% cruise unless there was a very high level of variability.  Tract size is important too.  On a 500 acre stand, a 10% line plot cruise requires 500 1/10th acre plots to give you a total of 50 acres sampled.  That is a lot of samples.  Contrast that with a 1 acre stand where you only would take one plot at a 10% sampling density.  If that plot fell in a part of that acre that was unrepresentative of the whole, your results could be heavily biased low or high depending on where that plot fell on the acre.  With 500 acres, that variability gets balanced out.  With one plot it does not.  

So, in general, the smaller the area to be cruised, the higher the sampling density.   Also, if the timber stand was highly consistent across the acreage, like a a plantation planted in rows, you could lower the sampling density.   The degree of variability is the most important factor in establishing the sampling density.  

[SwampDonkey]

The rule of thumb we practice is a minimum of 3 samples per stand and 1 sample per 100 meters in NB with a 2 m²/ha prism. But that goes back to college, and may be written somewhere. Been 25 years since I had to cruise timber in BC and reference their manual. :D I know some cruises in BC we have done 50 meter spacings. But in NB 100 m spacing is common practice. The spacing is also practised in NB for regen surveys, plantation survival, herbicide plots, as well as pre and post spacing surveys. One would typically type out stands with recent cutting activity from one not disturbed for years, even if both stands are sugar maple. A stand might have had a commercial thinning 2 years ago for instance. Maybe there is a creek buffer and then the same forest type continues, but undisturbed. A perimeter harvest trail is a common boundary between stands sometimes.

[Clark]

If you want an "accurate" cruise then that will be determined by the variability of the stand and the number of points put in. Method of determining trees to measure or count as "in" will factor into the number of points you install.

Rules of thumb such as 1.5 plots/acre or 10% cruise are designed around specific timber types or regions and the desired outcome. Using any rule of thumb could give you a terrible cruise. Or perfectly accurate. No way of knowing until you start crunching numbers derived from the cruise.

Clark