So here's the general premise. We have a basin. That's the "biggest" measurement for essentially, a valley with a river/stream in it that all tributary streams drain into. These tributary streams, even down to the littlest ephimeral (short-lived, maybe only a few weeks) streams, each have their own "mini-basin," if you will. There are, of course, terms for all the sizes of basins, with the size of basin we will work on being about 10 km^2, which qualifies it as a watershed.
In this basin we have transects. Transects are sampling "lines" that have been put in by researchers; they usually run along the paths of easiest access and are generally parallel to one another. The amount of transect lines is determined by the amount of plots per line (and the size of plot) which usually comes from a calculation for desired sampling intensity. These intensities are usually not very big; at Clemson, we aimed for somewhere between 1.5 and 3 %. Then again, that was very standard terrain, with large portions of the samples being loblolly plantations.
At each point on the transect, a circular plot is constructed through the very high tech (not) method of the BA prism. Essentially, you take a prism out into the field with a desired diameter, stand at the middle of the plot, and look at every tree on that plot. If the tree through the prism, is not "disconnected" (you look at the trunk), then the tree is considered "in" the plot and measurements are taken. If the tree is disconnected, you do not consider it "in" the plot. The idea is that by measuring the trees counted "in" and out by the prism, you get the right distribution of smaller trees (which will be "in" when they are closer to you and not in when further) and larger trees (which can be "in" at further distances) for an expansion of the data from your plots to reflect on the samples as a whole. This sounds tenuous, but many foresters in the 1960's made their fame by calculating this way versus total enumeration (oh god, say it isn't so) and finding no significant difference.
Well, our plots are different here, a bit. First of all, they have more variation, and second of all, there are sensors within the plots themselves to measure very interesting stuff, like sapflow, air temperature, soil moisture, etc. Many of these measurements can be accessed remotely, however, they have to be "calibrated" by hand. For example, you can calculate remotely what the soil moisture content is, but you need to be on site to see how much of the soil is a nice thick O-layer of litter, which of course contributes to this moisture.
So what's the question to answer? The proposal is to establish a "budget" similar to an accounting budget of carbon assets (pools) and liabilities (fluxes). Carbon assets are measurements (in Mg C/hectare) of carbon in biomass (separated by grade from foliage to fine roots), litter/slash/swd/snags/downed snags/submerged snags, and soil (separated by fraction, which has to deal with its buoyancy, which relates to surface area per soil "particle" and fraction composition (mineral). This, of course, isn't just something you plug a "carbon-o-meter" into a tree or dirt to get. Some of these measurements, like the carbon in the O-layer of soil, are relatively easy to figure out (figure out the fraction of carbon in organic material, which is SOM/1.72), and you've got the weight of the SOC (soil organic carbon). Measurements of SOM are available from data which we can get wireless. Other measurements, such as C in biomass, including the tree bole, are harder to get, but can be determined in a similar way, and allometry (using species specific equations to determine the amount of biomass in say, the leaves, based on the amount in the bole, which is essentially just its volume-- pretty much like finding V of a cylinder, plus some annoying stuff dealing with forestry units (standards for how you measure V are different depending on which units you want to use).
Just like in accounting, if you look hard enough, you can calculate all your assets. But it's harder to determine your liabilities. Your liabilities change depending on the length of the term that you are evaluating, who you owe, what the interest rate is. Let's say I want to know how much the atmosphere "owes" the leaves in C. Do I look at seconds? Minutes? Days? Years? If I look at a longer term, then I have to consider-- shade leaves will take CO2 in a different manner than sun leaves. In some seasons, CO2 uptake is greater. Trees, like people, store up for a "rainy day"-- so tree health, individually, is important. Not to mention species composition, air shed, diameter, canopy cover, leaf area, and isotopic signature. All of these factors come into what to use to look at photosynthesis for just the leaves of the tree.... obviously all are important, but where to start? Do you start with the basics of photosynthesis and then work out-- looking at a "perfect system" and then deduct for flaws in LAI, isotopes, air shed... or do you start by looking at measurements of atmospheric CO2 and seeing how these change over time, and then trying to pick up how much of this is taken by plants based on what is taken by soil or litter....
In a way, I allude this question to having a really nice piece of art but no house. You want to display the art, but you need to figure out how-- do you build the house around the art, or do you build the house, and then try to fit the art in. Either way, you have nice art and you're getting a house, but it's the method of getting from A to B that makes the question hard to answer.
