trees/acre

[ashes]

Hello again, I was curious if it is possible to gain trees/acre from an angle guage cruise?

I guess my question is without measuring DBH on all "in" trees and breaking it down into diameter class TPA, can I use the "in" trees to calculate general TPA for a stand?
Thanks

[WDH]

Why not take a few fixed radius plots and count the trees?  That is an easy way to get a quick approximation. 

[ashes]

I have the fixed plot TPA for this stand. I was just wondering if there was some way of working with a prism or angle gauge to get a general TPA or if you have to break it down by diameter class.

I am trying to compare the two methods, but finding that in a lot of cases it's like apples to oranges. 

[Clark]

It's a case of different methods give you results that work better or easier for different comparisons.

FRP - Easily converts to TPA but BA requires more work

VRP - Easily converts to BA but TPA requires more work.

I'm sure SD will come along and straighten us all out, he seems to get a kick out of looms and numbers!

Clark

[woodtroll]

You have to have a dbh for a variable plot to give trees per acre.
Each tree is counted as 10 sqft (10 factor prism) for BA.
But each tree diameter equals a number of trees per acre.
The larger the tree the less trees per acre it represents.
If it is a mixed stand an average dbh will not work very well.
And Yes SD will likely come on and fill in any gaps I left.

How accurate do you want to be? 

[ashes]

Thanks for that.^^

That's what I thought, but wasn't sure. 

[ashes]

...and I don't have to be accurate at all ;) :D

but in all seriousness I don't have a great understanding of the prism sampling theory. I know how to use it, and what its purpose is, but I don't fully get why it works.

[Ron Wenrich]

This comes from our Knowledge Base.  You will find it in the "Extras" button above. 

https://forestryforum.com/cgi-bin/tips/tips.cgi?display:1010359154-3844.txt

This is a file on number crunching from a variable sized plot cruise, which is what an angle cruise is.  There are 3 parts to this article.  One is on the equipment, one on the cruise, and one on number crunching. 

I've written management plans using angle gauges.  I find them an extremely valuable tool.  You can calculate volume, trees/acre, and stocking density.  What you do with the information is where the art of forestry comes in.

[WDH]

In the prism method, each diameter class has a "limiting distance" that the tree has to be within to be counted, and this distance goes up as diameter goes up.  This makes it much more complex than a fixed radius plot where all trees are evaluated on the exact same limiting distance.  For a very large tree, the limiting distance can be significant.  This creates a real disadvantage when the woods are thick and you have to peer through the vines, the greenbriar, and the free standing 4 foot tall poison ivy (thanks woodtroll!).  It is easy to miss the big ones without a lot of traipsing around in the jungle because you cannot see them.

[ashes]

Ron, thanks for that breakdown, and you're right, it's all about what you can do with the data after you have collected it.

[SwampDonkey]

I can't add much. But a small footnote to WDH's thread about big ones. We were cruising on the west coast, and this was suppose to be in juvenile wood. But of course some sites have veteran trees on them like on many logged sites back east. Anyway, our point samples were 25 meters apart. We had one big old western red cedar vet near four sample plots, which was counted four times in the sweep at the four plots (BAF was 8 m²/ha or nearly 35 ft²/acre). This thing was huge, we used 7.5 meter long d-tapes, it required 2 to get around the girth at dbh.  Of course we only measured it once. This was through thick salal vines that stay green year round. ;D

http://www.slugsandsalal.com/plantdb/shrubs/salal.html

[Ron Wenrich]

No one says you have to use a variable point with a BAF of 10.  You can use 5, 10, 20 or 40.  The angle gauge I have has all 4 built into one gauge.  You change your factor to match your conditions.  I tossed my prism decades ago.

[ashes]

yeah, a relaskop works best, but I have used all kinds. We sample with BAF of 40 for these trees. seems to be the prefered here, but I was curious if there was a method for knowing when to set it up or down, or if you just ask a forester in the area.

[woodtroll]

Ron is spot on for some plots it is vary handy. I used it 90% of the time with a small fixed plot for regen.
A angle gauge is not expensive and can be replicated. I have cut them out of plastic from chainsaw oil jugs and given them to contractors.  The told them what stocking range to thin to and how to check.
The fixed plot is nice for smaller trees, and regen.

[SwampDonkey]

Ashes, it depends on the timber as to what BAF you use. If it's too low your going to be doing a lot of extra measuring in big timber. ;D