Faster P cycling upon permafrost collapse

Permafrost collapse is expected to accelerate carbon (C) release and induce a positive C-climate feedback. As the frequently limiting key element in permafrost ecosystems, phosphorus (P) could mediate ecosystem C balance by modulating microbial decomposition and primary production. However, little is known about the changes in P cycling upon permafrost collapse. By combining sequential extraction, ³¹P NMR spectroscopy and metagenomic sequencing, we explored whether and how different soil P pools and microbial P transformation genes responded to permafrost thaw based on six thermokarst (abrupt collapse of ice-rich permafrost)-influenced sites on the Tibetan Plateau. We observed a significant decrease in soil labile P, NaOH-Po and residual P after permafrost collapse. The negative relationship between aboveground biomass P content and the soil labile P as well as NaOH-Po indicated that the reduction in these P pools were associated with the plant P uptake. Moreover, the increased relative abundance of the genes involved in inorganic P-solubilization and organic P-mineralization upon permafrost collapse reflected the potential increase in microbial P mobilization. These findings highlight a faster P cycling through plant P uptake and microbial P mobilization after permafrost collapse, which could impact the ecosystem C cycle and its feedback to climate warming.