Accounting for pathways in the carbon cycle is now much like the state of cosmology before big telescopes: Hubble saw something in data, and, a few twists and turns later, PRESTO – the Big Bang Theory. Much if is not most of Earth's biosphere carbon stores reside in forests, either above ground or in soil. Being that I live in a forest (Sequoia sempervirens, Psedostugs menziesii, Quercus sheevei), and being that I attempt (vainly, perhaps) to manage organic matter accumulation on my roof (failed, miserably) and yard (difficult, but manageable), I can offer up a pathway observation which might be of note in illustrating the difficulty of modeling the carbon cycle. Acorn cups, acorn shells, and male catkins.
In the context I wish to broadcast, these four pathway compartments hold small stores of carbon, but the residence time therein is considerable, and thus in a model may be of sufficient magnitude to influence model verification. Oak acorns get eaten: the shells (pericarp) last for years. Their abundance is not minimal in some instances, but their decay rate seems glacial.
A modeler might not want to dwell on the problem of stored carbon contained in spent oak inflorescences, assuming the matter trivial. They, however, do not decay rapidly, they certainly last for more than a given year because in spring, when the oaks flower, for a period one can find last yr inflorescences scattered about after a big blow. Inflorescence parts are retained in the canopy for more than a single growing season.
Acorn cups of Q. shrevei seem to have a half-life that exceeds that of the acorn shells: perhaps by a year.
In redwood forest, the female cones of Sequoia sempervirens also behave much like Q. shrevei acorns: they are small, but last for years.
These little vignettes are just that – vignettes particular to a particular forest type. But the problem of vignettes is just that: in accounting for the carbon budget of forests, are little seemingly trivial stores such as acorn cups, female cones, and inflorescence remnants trivial, or do they warrant sampling. In my view, sampling the trivial pathways to demonstrate they are in fact trivial is not trivial.