Redwood Reader

Glomalin II
Here are three quick items to keep the pot boiling. The first is a USDA press release. The second is Dan's post about glomalin when he saw it. I include it because of Dr. James Trappes comment about ectomycorrhiza exuding a glue. Most references to this point have concerned arbuscular mycorrhiza. My feeling is that glomalin is a structural component of hyphae and will be similar across most or all species of fungi, or mycorrhizal types at least. The author of the third article asks for quantification after a random search of the topic.

Glomalin: The Real Soil Builder
By Don Comis
February 5, 2003
An Agricultural Research Service scientist now has more proof that she has found a key ingredient responsible for the well-known benefits of soil organic matter.
Sara F. Wright, a soil scientist with the ARS Sustainable Agricultural Systems Laboratory in Beltsville, Md., discovered glomalin in 1996 and named the substance after Glomales, the taxonomic order of the fungi that produce the sticky protein. Recently, she used a nuclear magnetic resonance imager to show that glomalin is structurally different from any other organic matter component, proving it is a distinct entity.
The fungi live on most plant roots and use the plants' carbon to produce glomalin. Glomalin is thought to seal and solidify the outside of the fungi's pipelike filaments that transport water and nutrients to plants.
As the roots grow, glomalin sloughs off into the soil where it acts as a "super glue," helping sand, silt and clay particles stick to each other and to the organic matter that brings soil to life. It is glomalin that helps give good soil its feel, as smooth clumps of the glued-together particles and organic matter flow through an experienced gardener's or farmer's hands.
Glomalin was long lost in humus, the organic matter that is often called "black gold." When it did turn up in humus measurements, it was thought to be a contaminant.
Glomalin is not just the glue that holds humus to soil particles, it actually does much of what humus has been credited with. Because there is so much more glomalin in the soil than humic acid, an extractable fraction of humus, glomalin stores 27 percent of total soil carbon, compared to humic acid's eight percent. It also provides nitrogen to soil and gives it the structure needed to hold water and for proper aeration, movement of plant roots and stability to resist erosion.
ARS is the U.S. Department of Agriculture's chief scientific research agency

From: Daniel B. Wheeler (dwheeler@ipns.com)
Subject: Glomalin: fungal exudate sequesters up to a third of soil carbon for 7-42 years Newsgroups: sci.environment
Date: 2002-09-08 11:34:48 PST
Some four years after it was first published, I have found new data on
soil sequestration of carbon at:
http://www.ars.usda.gov/is/AR/archive/sep02/soil0902.htm
Glomalin: Hiding Place for a Third of World's Stored Soil Carbon
I have not had time to read all of the data yet. But it appears that
glomalin, a protein exudate produced by Glomus arbuscular mycorrhizal,
which are associated with the vast majority of plants the world over,
are also responsible for tying up significant quantities of carbon in
soil for long-term.
Glomus is further interesting to me because Glomites, the earliest
known mycorrhizal fossil known from Devonian shales dating back 400
million years, just happen to document these near-Glomus fungi which
appeared at about the same time that terrestrial plant life started to
develop.
Glomus may also be the predecessor fungi for truffles and other
ectomycorrhizal fungi, which are extremely common in recent volcanic
soils. The researcher in the above mentioned article was amazed to
find the highest levels of glomalin in Hawaii and Japan: two places
where volcanic activity is on-going. Volcanic activity along the west
coast of the US is also common, as are a plethora of ectomycorrhizal
fungi. Perhaps these ectomycorrhizal fungi also produce glomalin-like
compounds. Dr. James Trappe has noted that truffle mycelium produce
glue-like substances (similar to glomalin?) which cause soils to
absorb more water and _may_ act as root prophylactics to root rots in
PNW forests.
Daniel B. Wheeler
www.oregonwhitetruffles.com

October 31, 2003 Crumb Trail
Dirt GlueAn unanticipated benefit to blogging for me comes from examining access logs for search strings used by others to find the Crumb Trail. Some are humorous or salacious but others are useful. I sometimes google interesting strings myself. Today I googled "glomalin methods". Crumb Trail was 40 or so links down the list so whoever did the search worked to find it. At the top of the list was a USDA page devoted to sharing techniques for measuring glomalin.
The following methods may be used to examine glomalin, an arbuscular mycorrhizal fungal protein, which is ubiquitous in the soil and has been found coating fungal hyphae and soil aggregates. Because of its importance in forming water-stable aggregates and in soil fertility, concentrations of this protein are being measured in a variety of soils to compare soils of different compositions and/or tillage or disruption practices. Please refer to the listed references for further details concerning the methodology and results.
There was also a link to a glomalin information page
Soil aggregation is a complex process that is largely dependent upon microorganisms to provide glues that hold soil particles together. These glues are carbon-containing compounds that protect microorganisms from drying out. We are beginning to understand the importance of one group of soil fungi and the glue that is produced in large amounts by these fungi. The fungi are the arbuscular mycorrhizal fungi (AMF) and the glue was named glomalin after Glomales — the taxonomic order of this group of fungi..
Glomalin concentration and aggregate stability are related over 3 years during conversion from conventional tillage (P-T) to no tillage (N-T) corn (Fig. 3). A comparison was made with a perennial grass that grew undisturbed for 15 years as a buffer around the plots. Increases in both stability and glomalin were seen at yearly intervals, but had not reached the levels in the undisturbed grass. Higher levels of glomalin give greater water infiltration, more permeability to air, better root development, higher microbial activity, resistance to surface sealing (crusts) and erosion (wind/water).
Marvelous stuff. If we stop plowing fields will be more fertile with more organic matter, retain moisture as well as drain well and make better use of phosphorous and so need less fertilizers. Soil life will increase and plants will thrive.
Croplands will never be as healthy as grasslands but we can do much better. It is worth noting that soils get better year after year when left untilled as glomalin increases. It might be interesting to attempt to quantify the amount of carbon that can be sequestered this way since glomalin is so durable, accumulating year after year rather than cycling back to the atmosphere.