Please help figure out problem :(

T4Tree · March 17, 2012, 07:23:10 PM

Hi folks,

First of all I want to thank you for approving my request to be on this forum. I am new to the forum and somewhat new to Forestry. I am currently studying and majoring in Forestry.
I have a problem in one of my forestry classes that my professor gave me to solve and I've been beating my head against the wall trying to figure out. And I'm hoping someone here can help me.

The problem states:

Predict a 20 years into the future from a 6k acre tract of land of a 20 year old slash pine plantation with 600 stems per acre and a basal area of 100 square feet per acre. The average height of the dominant and co dominant trees is 60ft with a site index of 70ft at 25 years.
I am also suppose to determine how much pulpwood the tract of land will produce in order to feed a paper mill. The mill will accept woof from a 4'' top to a 20'' top, however the firm gets a better price for sawlogs therefore wants anything 12'' or larger to go to the sawmill.
Another given states that the current stumpage is $150/thousand cubic feet.

I think I figured out how to do the first part but the second part of determining how much pulpwood the land will produce and what to send to the sawmill and what goes to the paper mill, has been making my head hurt. I just can't seem to figure it out. Is there an easy way of doing this that I'm missing? It's something I definatly need to learn to get into forestry and would appreciate and leads on this anyone will be wiling to give.

Thank you in advance.

snowstorm · March 17, 2012, 08:30:08 PM

you should do your own homework... thousand cubic ft????????

T4Tree · March 17, 2012, 08:41:18 PM

Quote from: snowstorm on March 17, 2012, 08:30:08 PM
you should do your own homework... thousand cubic ft????????

Not asking for anyone to do my homework. Asking for help or a lead on how I can figure it out this problem.

beenthere · March 17, 2012, 08:45:38 PM

T4Tree
Welcome to the forum.
That response by snowstorm wasn't the Forestry Forum way of greeting new members.

Can you talk your way through the problem? Sounds like you have the numbers for the forest now, and an indication what the site will produce or grow per year. Figure what the site will add each year, and make some plots to help get some numbers on paper.

Lay out some of the info you know about now, and we can point or ask questions of your calculations.

Texas Ranger · March 17, 2012, 10:40:29 PM

Welcome to the forum. Most species, given the information you have, have a rule of thumb about the growth potential for each site index, by species. Say, 129 cubic feet per acre per year. These are general numbers, but we use them to base tax value on stands down here in Texas. Your mileage may vary.

Forestry Handbook should be on your shelf, or the library, and will be a big help.

Again, welcome aboard, put up a chair and set a spell.

WDH · March 17, 2012, 10:49:20 PM

One of the key clues is the site index of 70 at 25 years. From this, you should be able to get a stand and stock table that shows the number of stems by diameter class. There are tables for this. From these tables, you can determine the sawlog to pulpwood split using the diameters and a volume table. With 600 stems per acre at age 20, there will be very few sawlog sized trees.

One funny thing in the question is that a 20 year old slash pine plantation with 600 stems/acre and a BA of 100 is odd. At that stocking at that age, the BA would normally be higher. A stand 20 years old with 600 stems per acre will have small diameters, and would likely be all pulpwood.

Keep us posted!

zopi · March 18, 2012, 01:04:38 AM

Is a one hundred square foot basal area a little dense? I thought that seventy or so square feet was a good average target...

It seems to me that there are several layers to this problem...at some point the tract will have to be thinned, and beyond juvenile trees, any thinning should provide some pulp output, maybe in small bolts..but still viable pulp....I guess that should follow that rule of thumb, but it seems like it would be a non linear change...assuming steady average rainfall and no major bug kills anyway...

I don't know much about it...but it sure is interesting.

WDH · March 18, 2012, 08:05:18 AM

Many Foresters thin down to 70 square feet of basal area. I like to go a tad lower. 100 square feet is pretty dense, but not overly so.

Rocky_Ranger · March 18, 2012, 12:20:49 PM

This problem is wrong on so many fronts it must be a trick; first of all, my old SI tables are showing 60'@ 20 years to be 83 SI for slash pine. Couldn't find the base, but that seems close for an SYP. Then, 600 stems/acre at 100 BA at age 20? That's terrible, terrible! We had lob stands at age 20 with small sawlogs in the plantation - running 160 - 180 BA. This info gives an average DBH of only 5.52. 5.52! Thin that thing out our you'll never reach sawlog size in another 20 years. All you have here is a bunch of "pecker poles"; for growing biomass this may be the trick, but for sawlogs it ain't gonna happen.........

Ron Wenrich · March 18, 2012, 07:49:11 PM

I always thought the density on pine was much higher than that on hardwoods due to the compact tops. If memory serves, it was to thin to 120 and 180 was considered overstocked for white pines. We have very few pine plantations in PA, so, I stay out of the plantation questions.

Rocky_Ranger · March 18, 2012, 08:44:41 PM

I've seen 200 - 220 sq ft/acre in thriving plantations of loblolly (prior to thinning), but given the givens here I don't see how any of the stand could have over 20% live crown ratios. If ya thinned it heavy they'd (crop trees) probably lay over and kiss the ground. With basal area, given the numbers presented in the problem, they ain't much room for "wiggle".

zopi · March 18, 2012, 09:00:13 PM

I think too there is not enough valuable information...where is this stand located? Pacific northwest, and all the average height numbers are jacked? The swamps of the southeastern US and they are just dreaming? The maritimes? lol

See WDH..Iwas paying attention when you explained all that..

WDH · March 18, 2012, 10:05:41 PM

If it is slash pine, it has to be in the Atlantic or Gulf Coastal plain, probably in the flatwoods. Slash pine will stagnate if not thinned and if it is too dense. This plantation in the exercise has to be stagnated at that level of stocking and at that age. The stems have to be very small. Once stagnated, slash usually will not respond to thinning. The general prescription in the case of a 20 year old stagnated slash plantation is to clearcut and start over. You would never be able to produce sawlog sized trees in this stand with that stocking at that age.

Still, the basal area is way too low for the information given. It may very well be a trick question.

Texas Ranger · March 18, 2012, 10:55:05 PM

clear cut and replant, then work from a new base. I think they may be asking a Sylva culture question more than a production question.

If nothing else, it would be an alternative answer.

I always felt there were more answers to these type of questions then the profs would admit were there.

SwampDonkey · March 19, 2012, 06:23:44 AM

Hardwood is way thicker than softwood plantations because of shade tolerance. In thinning, if you want to call it plantation for the purpose of comparison, hardwood density should be 3000 st/ha (1200 st/acre), where as red pine,jack pine,spruce is 2500 or as low as 2000 st/ha (800 st/acre). Now white pine thinning they want it thick, like 4000 st/ha (1600 st/ac), but not for the reason you might think. It's because of the weevils, but that is just a farce because it doesn't work. White pine has to be interplanted with partial shade up here or it will be weeviled no matter what. And planting it thick is an assurance it with get rust. We have some plantations of white pine and they might be worth biomass, but nothing else.

I don't think the problem at hand here is a trick question. It's designed to see how you can analyze a situation and make reasonable projections based on what's presented. Often times that's the challenge, someone collects the data and someone else is left to work with it.

OntarioAl · March 20, 2012, 11:41:12 AM

T4Tree
As a Forester living and working in the Boreal Forest I can only dream of 60 ft 20 year old plantations.
My take on this problem is the landowner is looking to maximize their return on investment, (hint they want to sell as many 12" sawlogs as possible)
The Foresters that are familiar with slash pine say that this plantation been poorly managed and will not produce enough sawlogs by age 40.
Using yield tables for slash pine for the given site index set up a spread sheet comparing the annual potential cash flow over the next 20 years between starting over (clear cut) and trying to salvage a poorly managed plantation.
You will have to do some research on slash pine's response to release (which has been already stated as being poor) and apply a factor that allows for this in your projections.
Hope this helps
Al

T4Tree · March 27, 2012, 03:06:27 AM

First off I want to thank everyone who replied.

All I can say is wow, I didn't expect to get any help on this so I kind of abandoned the issue on the forum. I really appreciate everyones response and effort regarding this problem though. And I appologize for getting back so late.

Now about the problem, I turned it in to my professor a few days ago. I'm not exactly sure I did it right, however, I followed equations on establishing the mortality rate first then using a formula for the volume and basal area and finally using a specific distribution formula to calculate the amount that will go to sawlogs and pulpwood. I don't have the problem with me right now, but I would be willing to describe what exactly I did to solve it when I get it back if people are still interested. But like I said, I'm not sure if I did it right to begin with.

I want to again thank everyone who replied

WDH · March 27, 2012, 08:14:51 AM

I would like to know the answer. Yours, and what your Prof says is the "right" one.

chainspinrunner · March 28, 2012, 06:35:32 PM

T4Tree,
As a forestry graduate, I applaud you to turn to the forum for questions and answers, I have used the forestry forum throught 2 degrees in Forestry. I have cited the forum in research papers and gave credit where credit was due, which worked out great for me and some of my best responses came from the forum.

It seems as though you have had some good responses here and I am just as interested to hear your outcome.

Welcome to the FORUM!!!!!

Woodchuck53 · March 28, 2012, 08:57:52 PM

T4Tree, welcome you'll like it here. Yes indeed keep us posted on the outcome. I learn something new from these guys everyday I sign on. I'm anxious to here what your prof came up with and his remarks to how you arrived at your answer. Hang in there we will need all the forest people we can get. Chuck