Stimulation of primed carbon under climate change corresponds with phosphorus mineralization in the rhizosphere of soybean

Abstract

Elevated CO₂ and temperature likely alter photosynthetic carbon inputs to soils, which may stimulate soil microbial activity to accelerate the decomposition of soil organic carbon (SOC), liberating more phosphorus (P) into the soil solution. However, this hypothesis on the association of SOC decomposition and P transformation in the plant rhizosphere requires robust soil biochemical evidence, which is critical to nutrient management for the mitigation of soil quality against climate change. This study investigated the microbial functional genes relevant to P mineralization together with priming processes of SOC in the rhizosphere of soybean grown under climate change. Soybean plants were grown under elevated CO₂ (eCO₂, 700 ppm) combined with warming (+ 2 °C above ambient temperature) in open-top chambers. Photosynthetic carbon flow in the plant-soil continuum was traced with ¹³CO₂ labeling. The eCO₂ plus warming treatment increased the primed carbon (C) by 43 % but decreased the NaHCO₃-extratable organic P by 33 %. Furthermore, NaHCO₃-Po was negatively correlated with phosphatase activity and microbial biomass C. Elevated CO₂ increased the abundances of C degradation genes, such as abfA and ManB, and P mineralization genes, such as gcd, phoC and phnK. The results suggested that increased photosynthetic carbon inputs to the rhizosphere of plants under eCO₂ plus warming stimulated the microbial population and metabolic functions of both SOC and organic P mineralization. There is a positive relationship between the rhizosphere priming effect and P mineralization. The response of microorganisms to plant-C flow is decisive for coupled C and P cycles, which are likely accelerated under climate change.

Keywords: (13)CO(2) labeling; C degradation; Climate change; P fraction; P functional genes; Priming effect.