Temperature response of organic carbon mineralization in lake sediments of the Qinghai-Tibetan Plateau is dominated by substrate chemical composition and bioavailability

Lake sediments harbor substantial organic carbon (OC) reserves and exhibit remarkably high carbon fluxes, exerting a disproportionately large influence on the carbon cycle relative to their surface area. Now, the stability of lake sedimentary OC pools is increasingly threatened by ecosystem warming. Key questions remain unresolved: How does temperature influence the mineralization and turnover of OC? What mechanisms primarily drive the temperature response patterns of lake sediment OC pools? To address these gaps, we selected 13 lakes from the rapidly warming Qinghai-Tibetan Plateau (QTP) as study sites, and investigated the temperature response patterns of sedimentary OC mineralization processes by using microcosmic incubation, absorption spectroscopy, MALDI-TOF-MS, high-throughput sequencing and OC fractionation, etc. Our results reveal that in the QTP saline lake sediment environments, the stability and temperature response of OC pools are governed primarily by the chemical composition (e.g., chemical recalcitrance, molecular weight distribution) and substrate bioavailability (e.g., concentrations of dissolved and insoluble OC) rather than by mineral protection. Labile, carbon-rich organic compounds exhibit higher reactivity and temperature sensitivity during mineralization, challenging the predictions of the Carbon Quality-Temperature (CQT) hypothesis. This study discusses for the first time in lake sediments the relative importance of substrate bioavailability, OC chemical composition, and mineral protection on the temperature response patterns of mineralization processes, and provides multidimensional evidence through spectroscopic, mass spectrometric and other analytical techniques. In the context of climate warming, these findings can help us to predict more accurately the evolutionary trends of lake OC pools.

 

 

Key words: Lake sediments, organic carbon mineralization, temperature, chemical composition, substrate bioavailability, climate warming.