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Resource: used or used up in processes

Soil aggregates

Appears in 11 processs and 19 steps. Everything below is linked: open a process to see it in context.

Top processes

Aggregate formation and pore structure

3 steps

Bioturbation: fauna remodel soil structure

3 steps

Wind erosion: saltation, dust emission and deposition

3 steps

Surface state sets erodibility: aggregates and clods larger than 0.84 mm are non-erodible, so aggregate stability and tillage state set the erodible fraction
Loss of fines and organic matter coarsens the surface and weakens aggregates, raising erodibility
Coarse lag and non-erodible aggregates armour the surface, so loss slows once the erodible fraction is exhausted

Freeze-thaw cycling and soil structure

2 steps

Soil disturbance (fire, tillage, drought) and recovery

2 steps

Shrink-swell cracking and self-mulching in smectitic soils

1 step

Surface crumbs fall into cracks (self-mulching) and mix material downward while swelling pushes material up

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Microarthropods: springtails and oribatid mites as fungal grazers and litter processors

1 step

Faecal pellets increase surface area and microbial colonisation and form organic microaggregates

Earthworm drilosphere: gut passage, casts, middens and greenhouse gas effects

1 step

Casts dry or age into compact, water-stable aggregates that physically protect organic carbon

Gas diffusion and air-filled porosity control of soil aeration

1 step

Aggregates wider than roughly 5-10 mm can hold anoxic cores in wet soil because O2 diffusing through water cannot meet microbial demand

Soil compaction: stress, density, root limitation and recovery

1 step

Bulk density rises and porosity phi = 1 - rho_b/2.65 falls (1.3 to 1.6 g/cm3 takes porosity from 51% to 40%), mostly at the expense of macropores

Infiltration and surface partitioning of rain (rain intensity vs 1-1000 mm/h soil capacity)

1 step

Raindrop impact seals the surface into a crust and cuts infiltration several-fold

Often found with

Soil aggregates 11 Pore space 6 Water 3 Earthworms 3 Soil organic matter 3 Tillage 3 Frost 2 Ice lenses 2 Soil 2 Oxygen 2 Carbon 2 Soil microbes 1

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