Arbuscular mycorrhizae, glomalin, and soil aggregation

Arbuscular mycorrhizae are important factors of soil quality through their effects on host plant physiology, soil ecological interactions, and their contributions to maintaining soil structure. The symbiosis is faced with numerous challenges in agroecosystems; in order to inform sustainable management strategies it is hence a high priority to work towards mechanistic understanding of arbuscular mycorrhizae contributions to soil quality. This review focuses on glomalin-related soil protein (GRSP), operationally defined soil C pools that have been linked to arbuscular mycorrhizal fungi (AMF). In discussing this protein pool, we propose a new terminology used to describe fractions of soil proteins and glomalin. GRSP concentrations in soil are positively correlated with aggregate water stability. GRSP has relatively slow turnover in soil, contributing to lasting effects on aggregation. Controls on production of GRSP at the phenomenological and mechanistic level are evaluated. While there are significant gaps in our knowledge about GRSP and glomalin (particularly at the biochemical level), it is concluded that research on GRSP holds great promise for furthering our knowledge of soil structure and quality, for informing suitable management, and as a foundation for novel biotechnological applications in agriculture and beyond.