Quadratic Height Factor

[SwampDonkey]

Ok, so I had a guy ask me what quadratic height factor represents.

Fqi = Hi^2(Fti)

quadratic height factor = Tree Height squared times tree factor.

so what use it that?

Beats me

[Tillaway]

Shoot I struggle with SDI, Stand Density Index, and I know what that means... I think.

Thats a new one on me.

[SwampDonkey]

Here is one study by USDA using q-factor to predict tree height growth and species diversity in uneven aged management. From what my research has discovered its used mostly in managing hardwood stands, since they are long lived with varying degrees of shade tolerance. Would be applicable to west coast conifer species too I suspect.

http://216.48.37.142/pubs/viewpub.jsp?index=5834

http://216.239.39.104/search?q=cache:TtaTpJ9_bAQJ:efotg.nrcs.usda.gov/references/public/VT/VT666-0504.pdf+q-factor+tree+guide&hl=en


Here is the application of q-factor I think everyone uses. My original formula comes from Husch,Miller and Beers 'Tree Mensuration' and is different then this.

http://www.esf.edu/centerweb/bridgen1.htm

'The value of a stand q-Factor, a ratio of stems by diameter class and a descriptive term of stand structure, was determined. The q-factor was determined by dividing the number of stems per acre in any one diameter class by the number of stems in the next larger diameter class, and averaging across all classes.'

There are quides out there some place, apparently, but I've never seen them. I still think its pretty 'hokus pokus'

[Ron Scott]

Yes, the "q" factor is used in manageing hardwoods.

The "q" factor is an interesting term. The "q" doesn't really stand for anything. It's just a name given to the factor that expresses the relationship between diameter classes.

Stand tables should be compared to q-curves to determine how the diameter distribution in your stand compares to the "ideal" distribution. Thus you can see which diameter classes are over-represented and where, "ideally", you should
concentrate your marking.

The word "ideally" is one of the aspects that makes timber marking both difficult and fun. We have to apply a good deal  of thought.

This is somewhat complicated, so don't ask me to explain it.  

[etat]

No problem, I understand completely!

[SwampDonkey]

I've never seen q-factor applied here, but this one lad I mentioned above has taken the course on Hardwood Management in NE US and that is where he learned it. We base tree marking mostly on age, site, species composition, basal area, quality and diameter distribution. When applying diameter distribution we general want to avoid any type of diameter limit cut.  For some reason when you read alot of the literature on high grading they suggest that all of the largest trees are the best. And folks take that quite literally.   I look at the potential of the stand and the spacing of potential crop trees. We don't have many hardwood stands up this way with more than 30 m^2/ha (30 cord/acre) and that is above average because of cutting history. We have the potential for 40 cord/acre stands and I have seen one on private land. Wasn't especially large diameters, just tall trees on a rich site, and dense, 95 % sugar maple. If you have alot of mature yellow birch in the stand you won't get it because they require a larger crown space. Cedar stands on a good upland site, grow way more volume (60 + cords/acre). Pole sized hardwood stands are becoming hard to find on private land. Its going to get harder to find since farmers are looking to clear 10,000 acres for potato production which was lost or inaccessible due to the new 4 lane highway.

So it looks like my original post pertaining to quadratic height factor is totally different than what was ment by q-factor. Too complicated, stick with simple stuff ya can see by looking at the trees.

[redpowerd]

Pole sized hardwood stands are becoming hard to find on private land.

why is this?

[SwampDonkey]

Cutting history...........clearcutting, fragmentation and high grading on private lands. And some areas on gullied, steep, terrain and inaccessible.

Pole size ( 4-10 inch diameters)