Hypotheses

Grazing is selective: protists reject large, filamentous, pigmented or toxic cells, so gra → Aerated upland soils with high-affinity methanotrophs take up atmospheric Methane: global

Selective protist grazing of high-affinity upland methanotrophs sets their standing stock; suppressing protists raises atmospheric CH4 uptake in upland soil, and edible vs inedible methanotroph strains decide the response.

How to test it: Upland forest soil microcosms at 2 ppm CH4 with protist-depleted vs intact communities; measure CH4 uptake, pmoA copies and 18S protist shifts.

Prior work: 28,125 papers on the first topic, 3,456 on the second, 2 on both. Status: partly tested. Still untested: Upland soils with high-affinity methane oxidizers. Grazing is shown in rice soil.

Web search: No direct evidence. No study of protist grazing on upland methane oxidizers. Upland methane uptake is mostly explained by soil moisture and diffusion, and grazing does not appear in that work. Upland forest methane uptake, 2026 abstract

Why this chance: Grazing of methane oxidizers is shown in rice soil, upland is untested, and slow-growing upland oxidizers may be limited by other things. (A rough judgment, not a measured probability.)

Grazers carry spores and bacteria on cuticles and in faeces, changing which fungi colonize → Denitrifiers reduce nitrate stepwise via nitrite and nitric oxide to nitrous oxide and din

Collembola ingest nitrate-reducing bacteria and, as in earthworms, emit N2O from the anoxic gut in proportion to nitrate and density; antibiotic-treated springtails emit much less.

How to test it: Folsomia candida on 15N-nitrate-amended substrate; measure 15N-N2O and 15N-N2 per animal with and without streptomycin and tetracycline.

Prior work: 2,696 papers on the first topic, 39,703 on the second, 3 on both. Status: partly tested. Still untested: Springtail gut N2O emission and the antibiotic test.

Web search: Plausible by analogy. No direct measurement of springtail N2O. Earthworm guts emit N2O, and antibiotics cut earthworm emission by 80%, which points to gut bacteria. Aquatic invertebrates emit N2O from anoxic guts. The Folsomia gut is dense with bacteria. Folsomia candida gutAquatic invertebrate N2O project

Why this chance: Springtail guts are anoxic and bacteria-rich like earthworm guts, but nobody has measured it. (A rough judgment, not a measured probability.)

Fresh ash and tephra (volcanic glass) falls and weathers within decades in humid climates → Disturbance reshapes the nematode community: tillage and fertilizer favour c-p 1 enrichmen

Ash deposition removes slow-breeding c-p 4-5 nematodes first and favours c-p 1-2 enrichment opportunists, with recovery tied to ash thickness and allophane water retention.

How to test it: Ash-burial experiment (0, 2, 10, 20 cm) or chronosequence with nematode extraction and maturity index at 1, 6 and 24 months.

Prior work: 1,280 papers on the first topic, 47,445 on the second, 3 on both. Status: related only. Still untested: Shifts in nematode life-history groups by ash thickness.

Web search: Supports half. After the 2011 Puyehue-Cordon Caulle ash fall in Patagonia, nematode numbers and soil enzyme activity dropped. That study did not report life-history (c-p) groups, so the claim about which nematodes go first is untested.

Why this chance: Fits known nematode ecology, so likely true, but part of it is expected from existing theory. (A rough judgment, not a measured probability.)

Lytic cycle: phage takes over the host, replicates and bursts the cell, with a burst of te → Methanotrophs oxidize Methane with methane monooxygenase in oxic layers and the rhizospher

Where methanotroph hosts are abundant, lytic phage infection removes a measurable share of methanotroph cells per day and lowers net CH4 oxidation until hosts recover; removing phage by filtrate swap raises CH4 uptake.

How to test it: 13CH4 soil microcosms (SIP) with and without virus removal (0.02 um filtrate swap) or mitomycin C induction; track methanotroph pmoA copies, virus-like particles and CH4 oxidation rate over 2 weeks.

Prior work: 1,031,458 papers on the first topic, 1,108 on the second, 1 on both. Status: related only. Still untested: Phage killing of methane-oxidizing bacteria and its effect on methane oxidation.

Web search: Mixed, no soil data. No soil study shows phage lysis lowering methane uptake. A bioreactor report says phage blooms can set back methane oxidizers, supporting the direction. A lake study found phages that carry a methane-oxidation gene, which hints at the opposite effect. Sediment work found viruses infect methanotrophs but their genes do not directly drive methane metabolism. Viruses, methanogens and methanotrophic archaea

Why this chance: No soil data; evidence for and against the direction. (A rough judgment, not a measured probability.)

Lightning splits N2 into nitrogen oxides → Bacteria and archaea

Beyond fixing N2 into nitrogen oxides, lightning discharges that reach the ground permeabilise soil bacteria (electroporation) and move free DNA into competent cells, so lightning-strike zones should show raised horizontal gene transfer and altered bacterial community composition compared with matched unstruck soil.

How to test it: Sample soil along fresh strike paths and fulgurite margins versus paired controls; metagenomic comparison of mobile genetic elements, plus laboratory arc-discharge on soil with a marked plasmid.

Prior work: 3,420 papers on the first topic, 23,127 on the second, 1 on both. Status: partly tested. Still untested: Whether real lightning strikes raise gene transfer in the field. The lab step is shown.

Web search: Supports in the lab. Lab-scale lightning moved genes into bacteria in soil, and lightning-competent soil bacteria were isolated. One estimate puts the affected soil at 2 to 950 cubic metres per strike. Natural field transfer has not been shown, and no study looked at microbes in fulgurites or strike zones. Lab lightning gene transfer in soilLightning electroporation and gene transfer

Why this chance: Lab mechanism is shown; detecting it at real strike sites is hard. (A rough judgment, not a measured probability.)

Ocean surface water evaporates, absorbing latent heat → Sodic soil: Na on exchange sites disperses clay when electrolyte is low

Within a few km of a windward coast, annual sea-salt deposition raises exchangeable sodium percentage and lowers aggregate stability of low-organic-matter soils compared with sheltered inland sites.

How to test it: Transect from the surf zone inland: measure Na in bulk deposition, exchangeable sodium percentage, and clay dispersion (turbidity test) in the top 10 cm; control for parent material and groundwater.

Prior work: 2,047 papers on the first topic, 872 on the second, 0 on both. Status: nothing found. Still untested: Whether coastal sea-salt deposition raises soil sodium and weakens aggregates. No paper matched this wording.

Web search: Supports half. Coastal soils do show more exchangeable sodium close to the coast, with soils nearest the shore past saline-sodic limits and 1.5-2 km inland not. One Egyptian transect showed no steady trend. No source measured aggregate stability, so the aggregate-weakening step is untested. French studyKorean transectSurabaya transect

Why this chance: The sodium rise near coasts is known; the aggregate-stability part is new but expected. (A rough judgment, not a measured probability.)

Vapour condenses on aerosol particles into cloud droplets, releasing latent heat → Soil CO2 efflux reaches about 98 Pg C per year globally, far above fossil emissions of abo

Years or days with more aerosol-scattered diffuse light (volcanic, smoke, thin cloud) show higher root-derived soil respiration 1-3 weeks later at the same forest, beyond the effect of soil temperature and moisture.

How to test it: Use flux-tower or automated-chamber soil CO2 efflux series across clear versus hazy days or the Pinatubo years; regress efflux on diffuse fraction with soil temperature and moisture as covariates; add a trenching or girdling treatment to separate root from microbial respiration.

Prior work: 1,000 papers on the first topic, 3,933 on the second, 2 on both. Status: related only. Still untested: Soil respiration response to aerosol-scattered light. The matched paper models carbon fluxes in smoke haze.

Web search: No direct evidence. Smoke haze with moderate aerosol raised canopy photosynthesis, which supports the first step. Nobody has measured the root or soil respiration response. A 2025 preprint calls the root-respiration link largely theoretical. Near volcanoes, geological CO2 can be mistaken for soil respiration. Smoke and diffuse radiation, 2019Root vs soil respiration, 2025 preprint

Why this chance: Diffuse light does raise photosynthesis; a root-respiration response is plausible but hard to separate from temperature. (A rough judgment, not a measured probability.)

Groundwater creeps toward rivers and coasts → Soil moisture, temperature and pH limit faunal activity

As sea level rise pushes saline groundwater inland, rising soil salinity cuts survival and reproduction of earthworms, enchytraeids and springtails in coastal soils, reducing bioturbation and litter fragmentation before plants show salt damage.

How to test it: Transects from fresh to salt-affected coastal soil (or a seawater-irrigation experiment) with fauna extraction, burrow density and litter-bag decomposition, plus EC and sodicity covariates.

Prior work: 3,864 papers on the first topic, 58,994 on the second, 2 on both. Status: partly tested. Still untested: Coastal field effects and the loss of bioturbation and litter breakdown. Survival and reproduction are tested in the lab.

Web search: Supports most of it. Mesocosm work shows enchytraeids drop at once under seawater intrusion, with delayed effects on earthworms and plants. Lab tests show salinity cuts survival and reproduction of standard soil invertebrates, including springtails. Bioturbation and litter breakdown in coastal soils were not measured. Seawater and NaCl on soil invertebratesSalinization of coastal ecosystems

Why this chance: Most of the fauna effect is already shown; the bioturbation consequence is the new part. (A rough judgment, not a measured probability.)

Volcanoes and ridges outgas Carbon dioxide and gases → Bacteria and archaea

Volcanic ash and gas deposition restructure soil bacterial and archaeal communities, with severity of burial and acidification predicting loss of diversity and a shift to pioneer taxa.

How to test it: Sample soils along an ash-thickness gradient after an eruption; sequence 16S rRNA, measure pH, sulfate, and nutrient release, and track recovery over years.

Prior work: 1,414 papers on the first topic, 11,231 on the second, 3 on both. Status: partly tested. Still untested: Whether burial depth and acidification predict loss of diversity.

Web search: Partly supported. Chronosequences show soil communities shift with age after eruptions, and acidophilic iron oxidizers pioneer fresh deposits. No study compared diversity before and after burial, so the severity-diversity link is untested. Soils of different ages after eruptions

Why this chance: Community shifts are known; the severity-diversity gradient is untested. (A rough judgment, not a measured probability.)

Industry, crop fixation and fuel burning add reactive N (Haber-Bosch) → Litterfall and root turnover supply organic matter to soil

Plots under elevated tropospheric ozone form about half as much new soil carbon per unit carbon input as plots without it, and the effect scales with local NOx emissions downwind of cities.

How to test it: Open-top or FACE fumigation of ozone at ambient +50% on young stands; measure litterfall, fine-root turnover and soil carbon formation by 13C tracer; compare along an urban-to-rural ozone gradient.

Prior work: 1,154 papers on the first topic, 18,674 on the second, 11 on both. Agents are still checking the closest papers.

Ocean currents carry warm water poleward → Soil moisture sets an optimum: dry soil limits cell activity, wet soil blocks diffusion

Interannual soil respiration at wet-forest sites rises in the El Nino phase through less waterlogging, and falls in dry-forest sites through drought, with sign set by site wetness.

How to test it: Multi-year automated chamber records across a rainfall gradient (e.g. Panama, Amazon, savanna) regressed on a lagged ENSO index with soil water as mediator.

Prior work: 5,838 papers on the first topic, 20,955 on the second, 16 on both. Agents are still checking the closest papers.

Filamentous cyanobacteria (Microcoleus vaginatus) pioneer bare dryland soil and bind parti → Surface warms as absorbed sunlight turns into heat

Mature cyanobacterial crust with scytonemin lowers dryland surface albedo enough to raise surface temperature by several degrees, altering evaporation and the surface energy balance at the scale of crust-covered land (about 20% of land).

How to test it: Paired albedo and surface-temperature transects on crusted vs scraped plots across a successional gradient, then upscale with satellite albedo masked by crust maps and compare in a land-surface model.

Prior work: 712 papers on the first topic, 17,600 on the second, 11 on both. Agents are still checking the closest papers.

Bdellovibrio enters the periplasm, forms a bdelloplast, grows as a filament and lyses the → Bacteria oxidize ammonia where ammonium is plentiful

Obligate predatory bacteria (Bdellovibrio, Myxococcus) prey on Gram-negative ammonia-oxidising bacteria and cut potential nitrification, most at high ammonium where AOB dominate.

How to test it: Add Bdellovibrio bacteriovorus to Nitrosomonas/Nitrosospira cultures and to ammonium-amended soil; track AOB amoA copies, nitrite output and predator counts.

Prior work: 1,954 papers on the first topic, 18,244 on the second, 10 on both. Agents are still checking the closest papers.

Microbial death, viral lysis and grazing return microbial N to the organic pool → High efficiency: more carbon becomes microbial biomass and necromass

Higher viral lysis rates lower community carbon use efficiency (more carbon respired by survivors, more released as necromass), so soil viral load helps set how much carbon is stabilized.

How to test it: Soil microcosms with phage-enriched vs virus-reduced (filtered, re-inoculated) communities, measuring 18O-water CUE, CO2, and amino-sugar necromass markers.

Prior work: 438 papers on the first topic, 1,693 on the second, 12 on both. Agents are still checking the closest papers.

Humification and SOM stabilization → Land, ocean and vegetation absorb sunlight

Gains or losses of surface soil organic carbon change bare-soil shortwave albedo enough to offset part of the climate benefit (or loss) of the carbon change.

How to test it: Spectrally measure albedo of paired soils across an organic carbon gradient at fixed moisture; compare radiative forcing of the albedo change with the CO2 forcing of the carbon change.

Prior work: 22,809 papers on the first topic, 3,233 on the second, 15 on both. Agents are still checking the closest papers.

Ocean currents carry warm water poleward → Carbon dioxide respired to air

El Nino years shift soil respiration through temperature and moisture anomalies, with sign depending on whether the region becomes drier (suppressed) or warmer and wetter (raised), adding to interannual CO2 growth variability.

How to test it: Combine soil respiration databases (e.g. SRDB, flux towers) with ENSO index lags; test the sign of the response by region and soil moisture regime.

Prior work: 5,838 papers on the first topic, 12,590 on the second, 22 on both. Agents are still checking the closest papers.

Roots draw soil water that leaves through leaf pores (transpiration) → Nitrifiers oxidize ammonium to nitrite and nitrate (nitrification)

Plant water uptake lowers soil water content and so changes ammonium diffusion and oxygen supply, making nitrification peak at intermediate soil moisture set by transpiration demand.

How to test it: Planted vs unplanted (or shaded) pots under controlled evaporative demand; track soil moisture, 15N-pool-dilution gross nitrification, and amoA abundance.

Prior work: 19,966 papers on the first topic, 15,637 on the second, 10 on both. Agents are still checking the closest papers.

Warming deepens the seasonally thawed active layer and thaws previously frozen organic mat → Mesofauna (mites, springtails) graze fungi and fragment litter

As the active layer deepens, springtails and mites in permafrost wetlands and tundra expand their abundance and depth range, shredding thawed litter and grazing fungi, so fauna accelerate thawed-carbon decomposition beyond what temperature alone predicts.

How to test it: Thaw-depth warming plots with faunal exclusion (mesh bags or heat extraction) measuring CO2 and CH4 flux and litter mass loss over 2-3 summers; compare to microbe-only models.

Prior work: 3,444 papers on the first topic, 58,311 on the second, 6 on both. Agents are still checking the closest papers.

Snow insulates: with conductivity 0.1-0.5 W/m/K, about 30 cm of snow can hold soil near 0 → Mycorrhizal fungi trade nutrients and water for plant carbon

Snowpack depth and snowmelt date, through soil insulation, control the timing of extraradical hyphal growth, so warming winters with thinner snow cause plant-fungus phenological mismatch that lowers mycorrhizal nutrient delivery in spring.

How to test it: Snow-manipulation plots (removal, fences, early melt) with minirhizotron and ingrowth-core hyphal production, 33P or 15N tracing through hyphae, and plant uptake timing.

Prior work: 4,262 papers on the first topic, 18,295 on the second, 13 on both. Agents are still checking the closest papers.

Winds and storms carry heat and moisture poleward → Bacteria and archaea

Tropical cyclones deposit large pulses of nutrient-rich green litter that raise microbial abundance but cut richness for years, shifting the decomposer community toward fast-growing copiotrophs and changing soil C and N turnover long after the storm.

How to test it: Before/after sampling of permanent plots across cyclone tracks; greenfall addition and removal plots with 16S/ITS sequencing, CUE and N mineralisation assays over 3-5 years.

Prior work: 7,311 papers on the first topic, 27,433 on the second, 14 on both. Agents are still checking the closest papers.

Symbiotic fixers convert Dinitrogen to ammonium, paying with photosynthate → Sorption and occlusion remove phosphorus from the cycle as the soil ages

Biological nitrogen fixation per unit fixer biomass is lower on old soils with high phosphate sorption capacity (oxalate-extractable Al+Fe) than on young apatite-rich soils, because sorbed phosphate caps nodule activity.

How to test it: Measure fixation (15N or acetylene reduction) in legumes along a Walker-Syers chronosequence and regress against oxalate Al+Fe and resin-extractable P.

Prior work: 1,933 papers on the first topic, 329 on the second, 0 on both. Agents are still checking the closest papers.

Shrubs trap more snow, insulating soil so winter soil stays warmer → Microbial mineralisation of organic N and P releases Ammonium and phosphate

Plots where shrubs trap deeper snow have higher winter net nitrogen mineralisation than neighbouring open-tundra plots, and the extra mineral N predicts shrub biomass the next summer.

How to test it: Snow fence experiment in tundra: measure winter soil temperature, 15N pool dilution mineralisation and subsequent shrub growth; compare with unfenced controls.

Prior work: 576 papers on the first topic, 1,283 on the second, 0 on both. Agents are still checking the closest papers.