Glomalin-related soil protein in colluvial soils as a proxy for reconstructing millenary changes in landscape and soil health

Glomalin-related soil protein (GRSP) is an operationally defined soil organic matter pool that includes a heat shock protein linked to arbuscular mycorrhizal fungi (AMF) living in symbiosis with most vascular plants and plays a key role in soil health. However, the potential of GRSP as a palaeoecological proxy remains unexplored. We analysed the GRSP content in a North-western Iberian colluvial soil profile encompassing the last 14,000 years. We aimed to 1) identify whether GRSP is preserved, and 2) investigate whether GRSP could be used as a palaeoecological proxy after comparing its record with palynological and pedoanthracological records that account for landscape change. The results showed shifting trends in GRSP content and its immunoreactivity with age suggesting that long-term changes in GRSP along the colluvial soil archive might be driven by factors other than post-burial degradation kinetics. Changes in GRSP content at millennial scales were related to changing landscape composition as reconstructed by palynology and anthracology. GRSP content was larger than average when vegetation consisted in mature woodland formations. On the other hand, GRSP decreased during phases of vegetation change: first, from the birch open formation to the oak woodland at the Pleistocene/Holocene climate transition; and second, from the oak woodland to a heathland due to Late Holocene anthropogenic impact. While the GRSP record in this colluvial soil alone cannot provide information regarding changes in the composition of vegetation, it delivers a broad overview of major landscape shifts related to large climate- and human-induced changes in vegetation. Hence, GRSP analysis can be a time- and cost-efficient proxy for identifying long-term landscape changes that impacted soil ecosystem's health in colluvial soils. The results obtained highlight the need of further GRSP research on other environmental archives, including lake and mangrove sediments, as well as peat, colluvial and seagrass soils.