Microbial Controls of Primed CO 2 and CH 4 Release From Soils and Sediments Under Warming

ABSTRACT Global warming is altering carbon (C) cycling in terrestrial and inland aquatic ecosystems. Yet it remains unclear how experimental warming and elevation (natural temperature gradient) jointly regulate priming effects (PEs) on organic matter decomposition in soils and sediments and thereby influence CO 2 and CH 4 emissions. We investigated temperature‐dependent priming induced by 13 C‐labelled glucose additions across a soil–sediment continuum in the Rongbuk River Basin on the Tibetan Plateau (3759–4550 m a.s.l.). Soil and sediment samples were incubated under two temperatures (7°C and 17°C) to quantify PE for CO 2 and CH 4 (i.e., PE‐CO 2 and PE‐CH₄). Labile C inputs induced consistently positive PE‐CO 2 in soils, with generally stronger responses in sediments. PE‐CO 2 ranged from 0.42 to 11 mg CO 2 g −1 SOC in soils and from 0.41 to 15 mg CO 2 g −1 SOC in sediments, whereas PE‐CH 4 ranged from −2.2 to 5.2 μg CH 4 g −1 SOC in soils and from 0.14 to 7.9 μg CH 4 g −1 SOC in sediments. Warming increased PE‐CO 2 but suppressed PE‐CH 4 . Higher‐elevation sites showed lower primed CO 2 efflux but larger primed CH 4 efflux than lower‐elevation sites. This indicates that warming effects on priming depend on the balance between oxidative and reductive C processing. High‐throughput amplicon sequencing targeting the 16S and ITS2 rDNA regions indicated specific effects on priming: bacterial community composition was closely correlated with rapid, substrate‐driven CO 2 priming, whereas fungal communities were indirectly linked to primed CH 4 through their depolymerization of organic matter. Together, CO 2 and CH 4 released by priming of organic matter decomposition arise from distinct but coupled microbial pathways across soils and sediments, whereas sensitivity to temperature decreased along elevation. These findings highlight the need to explicitly account for oxidative and reductive priming related processes when predicting C turnover and greenhouse‐gas feedbacks in high‐elevation terrestrial–aquatic interface systems under climate change.