cruising plots ; how many?

[Sprucegum]

New owner of 160 acre woodlot here. I signed a bunch of papers at the lawyer's yesterday and one of them was a cheque so I figure the place is mine now.
While waiting for this deal I have been reading up on cruisin' to determine exactly what I have. Some articles advise plot spacing at 200' , some say 300' , and one says 350'. I realize the closer the spacing the more accurate the sample.
Question:
Can I do the 350' first to get a general idea of what is there and then insert additional plot samples in areas of interest or will this just confuse me?
Which is more accurate - the fixed radius plot or the prism eliminater thing?
You all have already been a big help by letting me lurk here.

Thanks again

[Ron Scott]

Have you checked in the Forum's Knowledge Base under "Forestry" for cruising information. Ron W. has put some "good stuff" together.

See "Forum Extras", above right.

[sprucebunny]

Congratulations, Sprucegum  8) 8) 8)

I hope you have a great time in your woods over the years. ;D

[Ron Wenrich]

Personally, I like the variable plot.  Its a lot easier to use and a lot easier to do by yourself.  I don't like prisms.  I use an angle guage that I get from Ben Meadows.  Industructable and cheap. 

A plot every 200' would give you about a 10% cruise.  I use it for doing management plans, and inventories.  My numbers are pretty close, but it all depends on how good you can cruise.  I also draw a map when I do it to mark timber type changes. 

After the map is drawn, I use a dot grid to figure up the acreage.  Then I figure the calcs using the number of plots and the number of acres.  It works pretty good for me.

You can use any spacing you want, but the further apart you are, the fewer plots and the higher the risk for errors.  But, since you already own the land, there isn't any high need for accuracy.  If you do a more accurate one the first time, there isn't any need to do another one.

Depending on topography, I can run about 40 plots/day.  The further apart, the fewer you will do in a day.  Do it before the leaves come out. 

[SwampDonkey]

I would only add that it depends on the variablity of the woodlot. ie the different groupings (stands) of wood species. Hardwood, mixed, softwood, cedar swamp, wetland etc.  A good rule of thumb is a minimum of 3 plots per stand or 1 plot every 300-350 feet. Avoid putting plots on stand boundaries because they can over estimate volume for a  particular species.

As an example: I've seen this often with hemlock on the edge of cedar/hardwood stands. Get two plots out of five on the edge where the hemlock are and no hemlock in the middle 3 plots of the cedar stand. The volume calculates way more hemlock than is actually present. Just something to be aware of. As you say, the closer the spacing the better the chance you'll be able to capture the variablity of a stand.

The difference between fixed plot versus plotless (variable) sampling is that with plotless sampling the perimeter of the plot does not have to be marked, the wedge prism determines if a tree is in based on diameter and the refraction of light through a wedge prism that is ground to a certain angle. As the arc of the angle of the wedge prism increases with distance from plot centre, the tree has to be increasingly bigger in diameter to be counted.

[Sprucegum]

Have you checked in the Forum's Knowledge Base under "Forestry" for cruising information. Ron W. has put some "good stuff" together.

See "Forum Extras", above right.

Thanks for the tip. This forum is so good I never thought to look for "extras"
Now where are my readin' glasses

Its just starting to sink in that I own the place so I can take all the time I need to do as many plots as I want. I believe I will try variable plots every 200' and map as I go. I have almost 2 months before I worry about leaves blocking my view .

[Texas Ranger]

This may be overly simple, but.  You will need a 100" tape, a diameter tape, and a device to measure height, either total or merchantable.  (Hey, if your gonna do it, do it right)  If you use a variable plot (Which I use and like) you will need a prism.  You can spend a lot of money on the above devices, so for now, go with the cheapest alternative.  Sometimes, your local state forester may have some simple give aways that can help. 

A couple of other things that may help, wire point centers and flagging tape.  If you really get into it, a good GPS unit to record location.  I was involved in doing follow up cruises on company land as part of a continuing inventory and had to find points created years ago.  Some we could find, many we could not and just got as close as possible.  With GPS it is much easier.

I bought a device years ago where I could cruise by myself, it is a sonic point center where I could measure outside trees from the center, and measure if necessary.  A hypsometer of some nature would help, also a string hip chain for doing your distances.  You can put a lot of money into equipment.

[Ron Wenrich]

Here's what I use for cruising: 

http://www.benmeadows.com/store/product_group.asp?dept_id=1312&cat_prefix=5WB

A lot cheaper than a prism, and you can't break it.

[Tillaway]

Relaskop, laser and data recorder..... : oh... sorry.  The bottle opener, tree finder, ...errr angle gauge works alright on flat ground.  The cutters here call em that. ;)  Going cheap and working on a slope one of the "cruisers crutches" works better than the angle gauge.... at least for me.

The standard grid for plot spacing I use is; lines 20 chains apart, 2.5 chain spacing between plots on each line.  You double the plots by dropping line spacing to 10 chains.

You will get 32 plots in 160 acres with the 20 chain line spacing. This is usually enough get your sampling error below 15%.  We come pretty close to 10% with it most of the time.

You can play with these spacings to alter the number of plots.  Number each plot uniquely, usually line number then plot number, so that you don't have two plot "1"s for example.  It gets real confusing trying to figure out which plot "1" goes in which stand type later if you choose to stratify the stand.

(edit) I got half way to the store and thought... did I say 1.5 or 2.5?  Its 2.5 plot spacing.

[Frank_Pender]

Tillaway, did you remember the bread and milk? :D

[Tillaway]

Yep  ;D