Linkages between the temperature sensitivity of soil respiration and microbial life strategy are dependent on sampling season

The temperature sensitivity (Q10) of soil respiration (Rs) is crucial to assess the carbon (C) budget of terrestrial ecosystems under global warming. The Q10 changes along a climatic gradient as well as its seasonal dynamics remain unclear, and the underlying microbial mechanisms are not well known. Here, the seasonal Q10 of Rs at the northern, middle, and southern sites of a natural temperate mixed forest was examined. The mean annual temperature (MAT) of the sampling sites spanned from 0.5 to 4.9 °C. The Q10 pattern over the climatic zones was highly dependent on season, with Q10 increasing toward the southern region in spring and autumn, but having a similar level across the sampling sites in summer. In spring, Q10 was independent of microbial community composition and functions. Instead, spring Q10 increased with decreasing C availability from north to south, consistent with the Carbon-Quality-Temperature theory. In summer, Q10 was closely associated with the dominance of microbial r-strategy features, characterized by high copiotroph/oligotroph and labile/recalcitrant C degradation gene ratios. In autumn, however, Q10 was driven by the K-selected microbial communities, which might have been ascribed to the priming effects mediated by fresh plant litter. The seasonality of Q10 was site-dependent. The southern and middle sites had the lowest Q10 in summer, consistent with the Seasonal Plasticity Hypothesis, which predicts lower temperature sensitivity in warmer seasons. In contrast, the Q10 at the northern site remained stable during the growing season due to minor seasonal fluctuations in plant litter inputs and microbial community composition and functions. This work deepens our understanding on the complex relationships between Q10, carbon availability and microorganisms over spatial and temporal scales by translating microbial phylogenetic data into life strategies.