The size of it
From cores of soil, each about a teaspoon
- plants they came from
- marker genes read
- – DNA reads per core
- one pasture, sampled once
Worth knowing before anything else: this counts DNA, not bodies, and not activity. A microbe that is dormant, or dead but not yet decayed, still shows up — and in soil the dead share is not small.
What the DNA showed
The plant above picks the neighbours below
Every patch holds about the same amount of life, whichever plant is growing over it (p = ). Which organisms are there is a different answer: the cores group by the plant above them, by more than chance produces at this sample size (p = ). This is the finding that survives every check the study puts to it.
Each dot is one pair. Two cores under the same plant are more alike than two under different plants — on average, and with a great deal of overlap. The bar is the average, the whisker its 95% interval.
It is a food web, not a soup
A second marker gene picks up the organisms with more complex cells: fungi, protists that hunt and eat bacteria, and the microscopic animals that eat the protists. Predators being present is the difference between a system that is running and one that is merely inhabited.
The complex-celled share of this soil, across cores. "Other" is everything the reference database could not place, which in soil is never small.
And one number this study cannot explain
Turning ammonia into nitrate is one of soil's essential jobs, and here it is dominated by archaea — an ancient branch of life, separate from bacteria — to a degree that in farmed soil usually means one specific thing. The study tested that reading against its own data. It did not hold. Both the number and the test that undoes it are on the research page, in that order.
What this does not establish
A study this size can rule some things in and a great many things out. These are the ones worth stating before anybody quotes the rest.
- Why the archaea dominate. The tidy explanation was tested against every other common organism in the same soil and ranked of — unrelated groups track the archaea about as closely. Something moves them; it is not specifically the thing we proposed.
- That the farming is the cause. The one published study that sampled pastures the same way found no difference between organic and conventional management within itself (p = ). If management did not move the needle there, it cannot be the whole explanation here.
- That the soil is not simply acid. Acidity drives the same balance, and this soil's pH has never been measured — only mapped. The study argues from which kind of archaea turned up, which weakens that rival explanation without replacing a pH meter.
- Anything about rates. Every functional statement here is about which organisms are present and in what proportion. A gene that is present may be switched off. Nitrogen cycling was never watched happening in this soil.
- Anything about white clover. One core was taken under it. One is not a group.
Every abundant group of bacteria in this soil, placed by how closely it tracks the archaea. If the proposed explanation were the right one, the orange marks would be alone at the left. They are in a queue.
So: the plant shapes the community under it, and this soil is unusual. Why it is unusual is not settled, and this study says so at length rather than rounding it off.
Where to go from here
Research
The argument in full, with every chart and every caveat in the position it belongs: the census, what separates the patches, the headline number, the objection it invites, and the test it fails.
Methods
How each number was computed, which checks came back negative, and a closing section on what is not documented — including the parts of the laboratory work nobody wrote down.
Sources
Every external work this study stands on, each saying what it is used for here, checked at build time against what these pages actually name.