Evaluation of glomalin content and its relationship with aggregation in urban soils

Abstract

Organic matter plays an essential role in the aggregation of soil particles and thus in the development of a stable structure. Among the organic components, the role of glomalin, a glycoprotein produced by mycorrhizal fungi, whose content can be affected by various factors, including land use, has been highlighted in the formation of aggregates. In this work, the content of glomalin in 56 urban soils of Santiago de Compostela is analyzed, on different lithological substrates and vegetation (forestry, grassland and horticulture), and its relationship with the stability of aggregates is evaluated. Easily extractable glomalin concentrations vary between 0.8 and 9.6 mg g^-1 (mean value 4.8 mg g^-1, 8 % of soil organic matter), with no differences attributable to lithology or land use. No significant relationship of stability of aggregates in water is observed with glomalin, but neither with other forms of soluble C nor with total C, which is attributed to the high organic matter content of the soils studied, which exceed the threshold values ​​above of which organic matter no longer has appreciable effects on aggregation.