Interpreting Soil Map

[g_man]

I am looking at the VT USDA soil maps for my 170 A wood lot and need help figuring out what they are telling me. I am trying to figure out what might grow best and where. I have about 50% Vershire-Lombard Complex at various slopes shallow to steep, slope face N to NW, about 25% Buckland Fine Sandy Loam flatter area, and about 25% Peacham Muck or Cabot Silt wet to swamp.

One map gives the Forest Productivity Rating as 43 cubic feet per Acre per Year. This is the same for all soil types except the swamps which are not rated. Is this good, average, or poor ? And why is it the same for all soil types ?

Another map gives the Site Index for American Beech. They list the Buckland as 65 to 66 and the Vershire-Lombard as 65 or less. Why do they choose Beech? And again is 65 good or poor. Why so much variability on the Vershire-Lombard. It doesn't seem meaningful.

As point of interest is on the Buckland, which has the high Beech Index, I have mostly W pine with a mix of Spruce and Fir and a very little hard wood. There is lots of regen which is 80% or more softwood. What do I make of this ?

I guess my real question is should these maps be helpful to a non-forester like me or do I need a whole bunch of additional info and knowledge to make use of them.

Thanks for any help. Hope the question isn't to big.

[KBforester]

One map gives the Forest Productivity Rating as 43 cubic feet per Acre per Year. This is the same for all soil types except the swamps which are not rated. Is this good, average, or poor ? And why is it the same for all soil types ?

Its not bad. I'm not used to those Vermont soils, but from the sounds of it I'm sure they are heaps better than things in Downeast Maine. 43 cubic feet is about half a cord per acre/year. That's not bad. At least relative to my world.




Again I don't know about VT's soil system, but often they choose a tree that does the best, or is common on that site. It its a dryer soil, beech might make sense for a site tree, and it would also make sense that you have pine. Keeping in mind the soil folks aren't terribly interested in the fact that no one actually likes to grow beech.

I recommend only using soil maps to justify a decision, not make it for you. At least in a forested setting. Crops and fields are different. Take careful observations of the trees that exist. What looks the healthiest? Cut a few fir.... are the rotten inside? Use that method to pick a winner or eliminate the losers. Glance at the soils map afterward.

Soil maps ARE excellent for things you can't see with your eyes. If the soil type has a depth to water measurement, that can be extremely useful for planning seasonal harvesting. Could make the difference between planing a harvest for the summer or the winter.

[WDH]

The USDA NRC has tried to make using the soils information easy, however, soils are very complex systems and it is hard to pigeon-hole all of them in nice little boxes.  Probably the most useful characteristics are soil texture in the topsoil and the subsoil, the drainage class (soil color tells you this), and the depth of the soil.

Very sandy topsoils are not as productive as more loamy ones.

Having some fine texture (clay) in the subsoil makes it more fertile and holds water better as long as there is not too much clay.  Some is good, but when there is too much, the soil won't drain well and it is tough on tree root development and spread.

Deep soils are more productive than shallow soils, all things being even.  They are better if 4 feet or deeper to parent material. 

There are about a million different combinations of just these three characteristrics  .

[g_man]

Thanks for the replys. Let me ask the question that got me looking at the soil map in the first place. I have a section that looks like it was clear cut. Probably 15 to 20 yrs ago near as I can figure. Before I was owner. My recolection, as a hunter here, is before that it was all softwood. Now the initial whips and saplings have thinned themselves out. The pin cherry, w birch and popple (aspen) have been beat out by red maple and are falling over. What I am left with is 3" or so red maple maybe 15' to 20' tall over 3' to 5' balsam fir.
From other locations I know the fir grows well here if given room and light but anything older than 60 years has stump rot.
I am trying to decide if I want the fir over the red maple and so I looked at the soil map for help. Figuring I would go with what would grow best.
My thinking is that if I want the fir I need it to grow quick to avoid rot and should remove the red maple over story.
The soil map didn't help me decide.
Maybe I think about stuff to much but I enjoy it.

[Clark]

I recommend only using soil maps to justify a decision, not make it for you.

I think that is an excellent way of using much of the soil maps information.  The other valuable way I use them is to compare two sites, one that I know can grow species A and the other that I have a hunch can but is currently stocked with another species.

One other thing to remember is that the soil surveys that were used to create the maps were done at a pretty coarse scale so they do miss finer details.  Which means you may have a transition in the soil between two forest types or landforms that doesn't show up on the map, for example.

KB forester alluded to it but remember that the people making the maps probably weren't all that interested in the plants that grow in your area.  They like soils like I like trees and we both try to ignore the other...which they can do better than I!  If there is "supporting" money for the soils people it is likely aimed at agriculture, any information they give about trees is playing second fiddle to ag information.

Clark

[SwampDonkey]

We have soils classification here specific to forestry, but it's academic mostly. All ya gotta do is see what's there growing to know what will do well. If it a species that does sickly on the site than it's probably just an colonizer like aspen, here today gone tomorrow. If it's a long lived tree and it looks great than chances are it's at home. However, the growth potential is a little below average I would say, if you follow your map as gospel. Up here we get 0.5 - 0.7 cord/acre/year on good ground. I would use the maps and guidebooks, as just that, guides. The vegetation tells you a lot about a site. Put the books and maps down after doing the research and observe. ;)

Fir needs well drained ground to amount to much, red maple grows in a wider range of soils from damp swamp to dry ridge. I've seen big red maple in cedar swamps as well as hardwood ridges. I have never seen a big fir in a cedar swamp, however a well drained gulley on a hillside can have a 20"er.

[WDH]

What you have seen from the clearcut is the effect of the light seeded early colonizers that jump started after the disturbance.  There is a succession of species over time on any site, and the light seeded, wind blown seed type species will take over in the beginning, just like you see in this case.

[Phorester]

I wonder if Site Index (SI) would be more useful for you.  SI is a numerical scale based on how tall a particular tree species will grow in a certain number of years, called the "base age". Most SI tables are based on 50 years, some on 25 years.  So, if you are using a SI table with a base age of 50 years, and you have a SI of 60 for a certain tree on a particular site, it means that this tree species will grow to an average height of 60 feet in 50 years. The higher the SI, the more productive the site is. 

A general description and other info is here:  pubs.ext.vt.edu/2812/2812-1028/2812-1028.html

SI might already be available for you in your soils maps. 

[Ron Scott]

Yes, I would think that site index information would be more useful. It might also be good to sit down with your local NRCS forester or CD forester and have them explain the specific soil interpretations for your properrty for better understanding of what might be useful information.

[g_man]

Thanks for the help.
I probably should ask my county forester. That's a good idea. He is a pretty good guy.
The site index they gave was what prompted my question because it didn't seem useful. I thought I was missing something. On the site of interest they gave the index for beech only. They gave it as: less than or equal to 65. I thought that was pretty wide and not at all helpful. I don't know if that is 0 to 65 or 60 to 65. And I don't know how beech relates to red maple or balsam fir in soil requirements.

The other thing that bothers is that they rate the entire 170 A as 43 cubic fee per year per acre independent of the soil type. Maybe that is a number they use for all poorer soils, I don't know.  I don't know the actual productivity numbers but I have been here long enough to know that it is not the same everywhere.

[SwampDonkey]

It never is. I went and mapped my own drainage and the wetter land followed all the veins/traces patches and hints of where the cedar stood. Old stumps and my memory pretty much verified it anyway. Fir and hardwood on the well drained land and the in between land was dominated by aspen, balm and red maple with spruce and cedar scattered into it. I can go right to the edge of my fir ground and all the sudden the ground just a step beyond turns semi wet. Vegetation tells a lot of the story and I've worked on two types of classification and both systems come down to what's growing there. Ash grows everywhere, but the wetter stuff only supports the black ash. White ash grows anywhere a red maple and aspen tree grows on my ground because nothing is rapidly drained or very dry. It's all flat.