Increases in global temperatures due to climate change threaten to tip the balance between carbon (C) fluxes, liberating large amounts of C from soils. Evidence of warming-induced increases in CO₂ efflux from soils has led to suggestions that this response of soil respiration (R_S) will trigger a positive land C–climate feedback cycle, ultimately warming the Earth further. Currently, there is little consensus about the mechanisms driving the warming-induced R_S response, and there are relatively few studies from ecosystems with large soil C stores. Here, we investigate the impacts of experimental warming on R_S in the C-rich soils of a Tasmanian grassy sedgeland and whether alterations of plant community composition or differences in microbial respiratory potential could contribute to any effects. In situ, warming increased R_S on average by 28 %, and this effect was consistent over time and across plant community composition treatments. In contrast, warming had no impact on microbial respiration in incubation experiments. Plant community composition manipulations did not influence R_S or the R_S response to warming. Processes driving the R_S response in this experiment were, therefore, not due to plant community effects and are more likely due to increases in below-ground autotrophic respiration and the supply of labile substrate through rhizodeposition and root exudates. CO₂ efflux from this high-C soil increased by more than a quarter in response to warming, suggesting inputs need to increase by at least this amount if soil C stocks are to be maintained. These results indicate the need for comprehensive investigations of both C inputs and losses from C-rich soils if efforts to model net ecosystem C exchange of these crucial, C-dense systems are to be successful.

中文翻译：

---

变暖增加了富含碳的土壤中的土壤呼吸，而没有改变微生物的呼吸潜能

由于气候变化而导致的全球温度升高有可能破坏碳通量之间的平衡，从而从土壤中释放出大量的碳。在变暖引起的增加的证据CO ₂从土壤中流出，导致建议，土壤呼吸（的此响应ř_小号）将触发一个正土地C-气候反馈周期，最终升温地球进一步。目前，关于驱动变暖引起的R _S反应的机制尚无共识，并且来自土壤C储量较大的生态系统的研究相对较少。在这里，我们调查了实验升温对R _S的影响塔斯马尼亚草草甸的富含C的土壤中，以及植物群落组成的改变或微生物呼吸潜能的差异是否可能对任何影响都有贡献。在原地，变暖平均使R _S增加28％，并且随着时间的推移以及整个植物群落组成的处理，这种影响是一致的。相反，在培养实验中，变暖对微生物的呼吸没有影响。植物群落组成的操作没有影响[R_小号或[R_小号气候变暖的响应。流程驱动ř_小号因此，该实验中的反应不是由于植物群落的影响，而是由于地下自养呼吸的增加以及通过根状沉积和根系分泌物提供的不稳定底物的增加。由于变暖，高碳土壤中的CO ₂外流增加了四分之一以上，这表明如果要保持土壤碳储量，投入至少需要增加此数量。这些结果表明，要想成功地模拟这些关键的C密集系统的净生态系统C交换，就需要对C投入和富C土壤的损失进行全面研究。