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ARS Home » Research » Publications at this Location » Publication #111574
Title: UNUSUALLY LARGE CONTRIBUTION OF ARBUSCULAR MYCORRHIZAL FUNGI TO ORGANIC MATTER POOLS IN TROPICAL FOREST SOILS.

Author
item RILLIG, MATTHIAS - UNIV. OF MONTANA
item NICHOLS, KRISTINA - UNIV. OF MD
item Wright, Sara
item TORN, MARGARET - LAWRENCE BERKLY NAT'L LAB

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Organic matter in soil is very important for soil health and stability. However, large uncertainties are associated with the origin and composition of soil organic matter. A newly discovered product from a soil fungus is helping us understand inputs and residence time of a major contributor to organic matter in some soils. A ubiquitous fungus that is associated with roots of 90% of land plants contributes directly to soil organic matter through production of copious amounts of a glycoprotein. The fungi are called arbuscular mycorrhizal fungi, and the glycoprotein was given the name glomalin. We tested a tropical soil chronosequence spanning ages from 300 to 4,100,000 years for glomalin. Along the chronosequence a pattern of glomalin concentrations was observed with the highest level at 120 mg/g soil. In young soils, glomalin represented about 10% of soil carbon and nitrogen. Carbon dating of glomalin indicated that the residence time was several years to decades. This information will help us determine ways to increase and maintain soil organic matter for sustainable agriculture and sequestration of atmospheric carbon.

Technical Abstract: Large uncertainties are associated with the origins and composition of soil organic matter (SOM). Arbuscular mycorrhizal fungi (AMF) contribute indirectly to carbon storage by influencing soil aggregation, and plant physiology, and community composition. Here, we present evidence that AMF can also make large, direct contributions to SOM. We found glomalin, a recently discovered glycoprotein produced by AMF hyphae, in tropical soils in concentrations of over 120 mg g-1 soil. Along a soil chronosequence spanning ages from 300 yr to 4.1 Mio yr, we observed a pattern of glomalin concentrations consistent with the hypothesis that this protein can accumulate in soil. Carbon dating of glomalin indicated turn over at time scales of several years to decades, much longer than the proposed turnover of AMF hyphae. The concentrations we found, in young soils representing a substantial amount (ca. 10%) of soil carbon and nitrogen, suggest that glomalin may be important to consider in biogeochemical studies.