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Participant: part of or influencing processes

Soil organic matter

Appears in 34 processs and 67 steps. Everything below is linked: open a process to see it in context.

Top processes

Carbon priming, microbial efficiency and soil carbon sequestration

6 steps

Living soil system

5 steps

Cation exchange, pH and soil solution chemistry
Humification and SOM stabilization
Fate of plant-derived carbon in soil
and 2 more in this process

Cation exchange, pH and soil solution chemistry

5 steps

Humification and SOM stabilization

5 steps

Start: Decomposition products and necromass
End: Stabilized soil organic matter
Pathway of stabilization
and 2 more in this process

Clay mineralogy and organic matter set cation exchange capacity

3 steps

Exudate priming and microbial nitrogen mining

3 steps

Show 28 more processes

Volcanic ash weathering to allophane and imogolite (andic soils)

3 steps

Volcanic ash parent material, short-range-order minerals and Andosol carbon

3 steps

Micronutrient availability: pH, redox and plant mobilisation of Fe and Zn

3 steps

Mineral surfaces accumulate and protect organic carbon as soil ages

3 steps

Nutrient availability and leaching

2 steps

Base cation cycling (calcium, magnesium, potassium, sodium)

2 steps

Soil export to rivers and ocean: sediment, dissolved carbon and nutrients

2 steps

Wind erosion: saltation, dust emission and deposition

2 steps

Aggregate formation and pore structure

1 step

Polyvalent cations and oxides bridge clay to organic matter

Roots and rhizosphere

1 step

Rhizosphere priming of organic matter decomposition

Water infiltration, retention and movement

1 step

Water retained in micropores by matric potential (field capacity to wilting point)

Mycorrhizal fungi network

1 step

Fungal biomass and necromass enter soil

Organic matter decomposition

1 step

Priming by fresh carbon accelerates native organic matter loss

Biological coupling: organic matter and soil food web

1 step

Net soil carbon gain: stable organic matter increases

Soil sulfur cycling

1 step

Most topsoil sulfur is organic (ester sulfates and C-bonded S), often 90-95% of total S

Root exudate chemistry, fate and priming

1 step

Exudate priming and microbial nitrogen mining

Soil disturbance (fire, tillage, drought) and recovery

1 step

Heating makes hydrophobic coatings that distil downward and form a water-repellent layer

Permafrost thaw and release of frozen soil carbon

1 step

Cold, waterlogged soils preserve about 1,300 Gt of organic carbon because decomposition is frozen out

Microbial dormancy, the seed bank and resuscitation

1 step

Rewetting of dry soil or a substrate pulse produces a CO2 flush (Birch effect) from released osmolytes and revived cells

Soil compaction and loss of macroporosity

1 step

Poor rooting means less root carbon and fewer biopores, leaving the soil more vulnerable to the next load

Plant-available water from field capacity to wilting point

1 step

Organic matter adds only about 1.2 percent by volume of available water per 1 percent soil organic carbon

Soil respiration: temperature and moisture control and climate feedback

1 step

Labile carbon is used up, so respiration per unit soil falls after several years of warming (Harvard Forest soil warming, 5 degrees)

Matric potential and the soil water retention curve

1 step

Organic matter adds only a modest amount of available water, about 0.012 m3 per m3 per 1% organic carbon

White-rot and brown-rot fungi: two routes to lignin and cellulose decay

1 step

Partly oxidized lignin fragments and fungal melanin enter the dissolved pool and can become humic precursors

Mineral surface area, reactive metals and the saturation of mineral-associated carbon

1 step

Saturation: the mineral-bound pool approaches a ceiling set by clay plus silt and reactive metals, so extra inputs accumulate as particulate organic matter or are respired

Progressive nitrogen limitation under rising CO2

1 step

More nitrogen is held in long-lived biomass and soil organic matter

Chronosequence: limiting nutrient and nutrient source shift as soil ages

1 step

Intermediate age: P is shifted into organic matter and secondary minerals

Soil formation

1 step

Mineral surfaces accumulate and protect organic carbon as soil ages

Often found with

Soil organic matter 33 Carbon 25 Clay minerals 17 Nitrogen 10 Soil solution 9 Soil microbes 9 Plant roots 7 Clay minerals 6 Water 6 Aluminum 6 Minerals 5 Rhizosphere microbes 5

Known by 719 participants and resources across the map.