Science Forums 2

[Michaelangelica]

Originally Posted by malcolmf

Care please. That's soil carbon. Also the carbon in glomalin molecules is fairly insignificant (4-5% of total soil C at best)

Much of the other 2/3 is in humin (not same as humic acid), which roughly translates as stuff we know is decomposed organic matter but have no idea of its detailed origins. There may well be another couple of glomalins (in terms of importance) waiting to be discovered in humin formation.

This is out of date now, having been based on a large one-off expeirmental increase in CO2. More realistic gradual increases do not have a significant effect. (Klironomos et al (2005) Nature 433(7026) pp.621-4)

The bodies of living things (worms, bacteria, mycorrhizae, etc) contribute a lot less than 1% of total soil carbon. (Rillig et al (2001) 'Large contribution of arbuscular mycorrhizal fungi to soil carbon pools in tropical forest soils', Plant and Soil 233(2), pp. 167-177. Their role is more to make soil a dynamic environment, and in so doing to release global warming gases from it.


I am not, and no they haven't. Laura German catalogues a series of highly variable and sometimes mistaken beliefs in her chapter in Amazonian Dark Earths, a couple of which I mentioned in my response to Philip. Indeed, what have they been right about? What else besides the garbage disposal and land management strategies that produced dark earths? And in the case of terra preta (rather than mulata) the researchers are divided as to whether that was intentional. Until evidence of soil growth is produced, I think it more likely to be a misinterpretation of strong recovery under fallowing.

M

This is out of date now, having been based on a large one-off expeirmental increase in CO2. More realistic gradual increases do not have a significant effect. (Klironomos et al (2005) Nature 433(7026) pp.621-4)

What do you mean by this?

The bodies of living things (worms, bacteria, mycorrhizae, etc) contribute a lot less than 1% of total soil carbon.

No I don't think so.
I will get back to you with some sums

Glomalin, a recently discovered major component of soil organic matter, stores about a third of the world's soil carbon, offsetting industrial
pollution. This is according to a recent collaborative study by scientists
with the Agricultural Research Service and the University of Maryland
(U-MD) at College Park. The study was partially funded by the U.S.
Department of Energy.

The study was done by Kristine A. Nichols, a U-MD soil science Ph.D.
candidate and technician at ARS' Sustainable Agricultural Systems
Laboratory in Beltsville, Md., along with colleagues Sara F. Wright and E.
Kudjo Dzantor. Wright, an ARS soil scientist, discovered glomalin in 1996,
and Dzantor is a U-MD soil scientist.

Glomalin is a sticky protein produced by root-dwelling fungi and sloughed
into soil as roots grow. By gluing soil particles and organic matter
together, it stabilizes soil and keeps carbon from escaping into the
atmosphere. In an earlier study, Wright found that glomalin serves as a
corrective to global warming because it increases with carbon dioxide
levels.

[organicviticulture] FW: Glomalin, the Unsung Hero of Carbon Storage

Large contribution of arbuscular mycorrhizal fungi to soil carbon pools in tropical forest soils

Untitled

The Soil Makers
1.1 A Brief Look at Soil Zoology
The Fundamental Decomposers

Bacteria, 6 to 10 million per cm2 , or 3 500 kg per acre
Fungi, 1 to 2 km of hyphae per cm2 up to and more than 1000 species in a woodland, about 90% of all material produced by plants is broken down by decomposers


Pedators and Secondary Decomposers

Protozoa, feed on bacteria and fungi
10 million per m2 or
Amoeba a million per gram of soil
Ciliates ten thousands per gram of soil
or
3 grams per m2 in grassland soils
20 grams per m2 in woodland soils

Nematodes (round worms), feed on bacteria, fungi, protozoa and plant roots
10 million per m2 in grassland soils
30 million per m2 in woodland soils
or
1 gram per m2

Enchytraeids (pot worms) feed on dead plant material
300 000 m2 in moorland soil
200 000 m2 in grassland
or
50 and 35 grams m2 respectively

Tardigrades (water bears) 50 to 500 m2

Pauropoda 20 to 2000 m2

Molluscs (Slugs and Snails) feed on rotting vegetation mostly

(there are a couple of carnivorous species which feed on other molluscs)
approx. 15 m2 in grassland soils
approx. 450 m2 in woodland soils

Symphyla , feed on fungi,
up to 1000 m2 in grassland soils
up to 3000 m2 in woodland soils

Isopoda (Woodlice) feed on fungi, and dead plant material
500 to 1500 m2 in grassland soils
up to 3000 m2 in woodland soils

Diplopoda (Millipedes) feed on fungi, and dead plant material
approx. 20 m2 in grazed grassland
approx. 100 m2 in ungrazed grassland
100+ m2 in woodlands

Chilopoda (Centipedes) feed on insects an other soil arthropods

approx. 120 m2 in grassland
150+ in woodlands

Aranaea (Spiders) feed on other arthropods
480 m2 in Moorlands
200 m2 in Pasteur

Acari (Mites) feed on everything are very responsive to pH,

more at pH 5 than at pH 6, and more in 'Mor' soils than in 'Mul' soils.
100 000 to 600 000 per m2 woodland soils
2 gams per m2

Collembola (Springtails) feed on fungi and bacteria,

dependant on soil moisture and pore space.
40 000 to 70 000 m2 in grassland soils
up to 500 000 m2 in coniferous woodland.

Coleoptera (Beetles) up to 2000 to 3000 per m2
in ungrazed grasslands and heathlands, levels are considerably lower in arable soils.

Hymenoptera, Ants, live in the soil, feed on other arthropods and plants secretions, nectar etc. important soil movers, the mound building species (wood ants) create large compost piles which often remain after the ants have gone.

Gordon's Soil Ecology Page

A critical part of SOM is humus - a very fine, darkcoloured
collection of complex organic molecules.

Humus results from the microbial decomposition
of plant and animal material, to the point where
that material has lost all trace of its original
structure. Among the many virtues of humus are
its excellent water and nutrient-holding capacity,
its ability to bind toxins such as heavy metals, and
its role in holding soil aggregates together

.