Overview:

One goal is to collect data on the influence of the chemistry of the underlying geology on tree growth.  One approach would be to conduct soil surveys and get close to the same data (as rock chemistry). I'd take samples on top of the rock field and samples as far away from that area at the same time. I'd run both samples through experiments at the lab and see what data we find. For instance, if the sample close to the boulder is higher, much higher, in phosphates than the outer samples it would begin to prove your hypothesis (concerning variations in growth). We wouldn't have as precise data, but we'd be going in the right direction. On top of that UMASS has recently opened a state of the art soil science laboratory. 

Some of the things I plan to do is to dig several soil test pits and document what I find. There will be pictures and samples taken. I m going to then take the samples to the lab and sift out the particle sizes, run pH, phosphorus, nitrates, and anything else I can think of. I've already secured the lab at HCC for over the summer, to run my data analysis.  The initial site will be approximately 75 feet square.  Once it is sampled the procedure could be repeated at subsequent sites.  [Phil LaBranche]

Sampling Density:

The frequency of sampling depends on the purpose of the study. For example, if you want to make a contour map of soil properties and relate that to the growth rates of each tree, you may need a fine sample grid. If you want to characterize the entire stand as one unit, then the average of four soil pits is sufficient. [Lee Frelich]

If you do want to study the growth of individual trees, then for such a small site, you may have to extend your soil analyses beyond the edge of the stand, because the environment off the plot will influence the trees (i.e. edge  effect).  [Lee Frelich]

The final density of samples depends somewhat on the variability you
find in the early part of the sampling. I would start with a low density
grid, say every 40 feet and then add samples at 20 foot intervals or
perhaps 10 foot intervals in between if those initial samples show a lot of
variability, but stop at 40 feet if they are mostly the same. [Lee Frelich]

Sampling Site Design:

The site I'll start work on is about 73.5' square. I plan to even things out at 70' square.  I sketched out the plot and am going to place 5 pits and 10 corings.  I'm going to put a pit in each corner and 1 in the middle. Then, conduct a core sample in between. [Phil LaBranche]

A pit would consist of using hand tools to dig a hole about 1.5-2' wide and 2-4' deep. Some of the soil taken from the hole would be bagged for lab analysis later on. I'd also use the Soil Survey Manual to help determine other field data, and conduct a field test for texture and color. When everything was collected, the hole would be refilled and covered over to minimize the look of the disturbance. [Phil LaBranche]

For the soil description, it is important to note depth of hardpans (if
any), since they can limit the depth of tree rooting, which is a major
determinant of tree, growth rate, ultimate size and height because volume
of soil determines how large the root system can be. [Lee Frelich]

A coring, on the other hand, would give us less data, but also create less impact on the forest. I'd use a soil auger to core a hole about 3-4" wide and 3-4' deep. Some of the soil would be bagged for the same lab analysis as the full test pit soil. When I was finished, the hole would be filled in and covered over. Using these two methods together will still give us the quality data we're looking for, while drastically cutting down on the impact I'd be leaving on the site. [Phil LaBranche]

I have some recent experience digging a fairly narrow hole with spades down to a depth of 3ft+, and, I can tell you, in stony New England soil, it was NOT a pleasant experience. The rocks were very uniform in size, like flattened potatoes, and, at different depths, were maddeningly overlapped, I assume by the work of the last of those pesky glaciers. Now that I think of it, those large, flat stones may actually prohibit you from coring down to any depth. [Susan Benoit]

Soil Description and Analysis:

Probably early next week, I'll be talking to UMASS and begin
setting up the steps needed in order for me to use their new soils lab.
Talking to my professor today, about half of the tests I'm planning to run I
am going to have to do at UMASS, as HCC isn't set up for them. One of the
other issues I'm going to discuss with the soil scientist is what would be
good things to be looking for in the samples. I'm still reading through the
research papers I found online, but am looking to cover pH, nitrates,
phosphorus, potassium, calcium, magnesium, manganese, zinc, copper, boron,
sulfates, organic matter, cation exchange capacity, and soluble salts.  Is
there anything in the list that we could rule out? And is there anything to
add? I'll keep everyone up to date, as things progress.  [Phil LaBranch]

Nitrogen is a difficult nutrient to work with because it is the rate of
supply of nitrogen in the form of NH4 and NO3 to the roots that is
important for tree growth, not necessarily total N in the soil. Most soil
analysis labs can do extractable NO3 and NH4, but it is a separate analysis
from the other elements. Also, N availability in the horizon with the most
fine roots (less than 2-4 mm diameter) is more important than N elsewhere
in the soil profile.  [Lee Frelich]

I assume you will send the soil samples to ICP analysis (Inductively
Coupled Plasma), which is commonly used by soil labs and can give you
concentration of a dozen elements other than N for several dollars per sample.  [Lee Frelich]

You should be able to obtain an electronic copy from your library of a
paper I published recently:

Frelich, L.E. Jose-Luis Machado and Peter B. Reich. 2003. Fine-scale
environmental variation and structure of understory plant communities in
two old-growth pine forests. Journal of Ecology 91: 283-293.

This is an example of the type of fine scale analyses we do in the Midwest,
and we used 5 and 10m grids for the samples. However, we were examining
tree seedlings and small herbs. I don't think a grid that fine is always
necessary when analyzing trees.  [Lee Frelich]