Elevational variation and drivers of temperature sensitivity of microbial respiration
Moreover, we also found that Q 10 did not significantly vary along with the elevation. Similar result was also observed in a recent global meta-analysis (Li et al. , 2022) and several observation studies (Schindlbacher et al. , 2010; Xuet al. , 2014; Zuo et al. , 2021), suggesting that microbial response to temperature was similar among different elevational gradients. Such results did not support the microbial thermal adaption that Q 10 declines from low to high temperature site (or from high to low elevation) (Bradford et al. , 2019). Moreover, our SEM analysis revealed no significant direct and indirect effect from MAT on Q 10, suggesting that no significant influence of elevation and temperature onQ 10 in the elevational gradients. Since many studies predicted climate warming is faster at high than that at low elevation (Pepin et al. , 2015), the unifiedQ 10 means future climate warming will cause more C loss at the high elevation. Meanwhile, other studies reported different elevational trend of Q 10 thatQ 10 increased (Gutiérrez-Girón et al. , 2015; Kong et al. , 2022; Okello et al. , 2022; Zenget al. , 2022) or decreased (Lipson, 2007) along with the elevation, suggesting that the elevational trend ofQ 10 still need more studies to confirm.
In this study, the unchanged Q 10 along with elevation might be due to tradeoff between the directly negative effect from elevation and its indirectly positive effect. All these indirect influences were via the pathway of AccMR_0_perSC, showing that high elevation indirectly enhanced Q 10 via reducing AccMR_0_perSC. Low AccMR_0_perSC means low soil C quality and contributes to high Q 10, similar result was also observed in previous studies (Ding et al. , 2016). These findings support previous carbon-quality-temperature hypothesis thatQ 10 of low quality soil C is greater than that of the high quality soil C (Fierer et al. , 2006; Liu et al. , 2017; Wang et al. , 2018; Bradford et al. , 2021), and confirm that soil C quality is a good predictor ofQ 10 value (Davidson and Janssens, 2006).
In summary, elevational variation of soil microbial respiration and its temperature sensitivity in a subtropical forest in South China were assessed by using lab incubation experiment. We found that incubated AccMR increased from low to high elevation. However, significantly elevational trend of AccMR_MAT was not examined after adjusted by the field temperature, due to the tradeoff between increasing Soil C concentration and declining field temperature. We further found thatQ 10 did not vary significantly along the subtropical forest elevational gradients, the variation ofQ 10 was negatively dominated by soil C quality (AccMR_0_perSC). Since climate warming is predicted faster at high elevation than that at low elevation, C loss from high elevation might be accelerated in the future and need more attentions.