Glomalin and Contribution of Glomalin to Carbon Sequestration in Soil: A Review

Abstract

Arbuscular mycorrhizal fungi (AMF) improves the uptake of nutrients and water to the plants through mutual symbiosis. Only AMF produces glomalin related soil protein (GRSP). Acaulospora morroaiae, Glomus luteum, Glomus verruculosum, Glomus versiforme are the effective glomalin producing AMFs. Mixed primary forest, tropical rainforest, soil organic matter, clay soil, no tillage, quality and quantity of fertilizers, crop rotation, and water stable aggregates are also suitable to increase glomalin production. Glomalin is a glycoprotein that contains 30–40% carbon (C) which is assumed to be stable and persistent in soil. The glomalin can sequestrate more carbon in the soil due to its high carbon and aggregate stability. Greater aggregate stability leads to high organic carbon protection in terrestrial ecosystems. The lowest glomalin content (0.007 mg per gram soil) was found in Antarctic region, and the highest glomalin content (13.50 mg per gram soil) was observed in tropical rainforest. In agricultural soil, glomalin content varies between 0.30 and 0.70 mg per gram soil. The GRSP containing soil organic carbon (SOC) in deeper soil layers was 1.34 to 1.50 times higher than in surface layers. Glomalin can sequestrate 0.24 Mg C ha-1 in soil when present at 1.10±0.04 mg g-1. At elevated CO2 (700 µmol mol-1) level, easily extractable glomalin (EEG) and total glomalin (TG) were 2.76 and 5.67% SOC in the surface soil layer over ambient carbon dioxide (CO2) level. This finding indicates the effective function of GRSP C sequestration in soil under global environmental change scenarios. Glomalin can also protect labile carbon that can help regulating nutrient supply to the plants. No tillage practice causes higher AMF hyphal length, GRSP and water stable aggregate (WSA) compared to that of conventional tillage practice. The current review demonstrated that GRSP is an important tool for carbon storage in deep soils. Glomalin mediates soil aggregates, improves soil quality, increases carbon sequestration and crop production, and mitigates climate change.

Mycorrhizal effects on glomalin-related soil protein and chlorophyll contents in coffee plants in the Peruvian Amazon

“…The results obtained in the present study in the Peruvian Amazon, a tropical region, are consistent with those authors, and the treatments in which the coffee plants were not inoculated with AMF showed 61.6 mg g -1 of GRSP in the soil, whereas those inoculated with the Moyobamba AMF inoculum showed the highest value (69.1 mg g -1 ). Different results were reported by Hossain (2021), who conducted a review article on glomalin content in various environments and found that Treseder & Turner (2007) reported 13.50 mg g -1 of glomalin in tropical rainforest soils, while Rillig et al (2003) reported the lowest glomalin content in a desert soil (0.007 mg g -1 ). The glomalin content found in the present study was much higher than that reported in the literature, and this corroborates that there is colonization in non-inoculated coffee plants in the field.…”

Carbon stocks in coffee farms and secondary forest systems in the Peruvian Amazon rainforest

“…Our results on higher number of AMF spores on coffee without shade are analogous to those by Polo-Marcial et al ( 2023), who found that the abundance and richness of AMF, especially glomerospores, was higher in agroforestry systems than in secondary forest. The presence of AMF plays an important role in the accumulation of GRSP, a critical component of the hyphal cell wall (Hossain 2021). Therefore, mycorrhizal hyphae prominently promote enhanced accumulation and preservation of organic carbon in aggregates and soil C pool (Wang et al 2022).…”

A critical review of 25 years of glomalin research: a better mechanical understanding and robust quantification techniques are required

“…2b) (Wright et al ., 1996). In soil samples, Bradford‐reactive/immunoreactive SP abundance is not consistently correlated with measures of AMF abundance, and studies have found MAb32B11‐reactive proteins within non‐AMF‐containing glasshouse cultures (Rosier et al ., 2008; Holátko et al ., 2021; Hossain, 2021).…”