The fresh carbon (C) induced priming effect (PE) on soil organic C (SOC) decomposition is critical for global C cycling. Climate warming could raise absorptive roots production and turnover, and then increase the input of absorptive roots litter (ABRL). Therefore, it is urgent to understand the PE induced by ABRL under warming. We conducted a 210-day experiment by adding ABRL of Cunninghamia lanceolata into a C4 soil and incubating them at 19 °C and 23 °C. We found that adding ABRL caused positive PE throughout the incubation. At the early stage (ES: first 30 days), labile C compounds dominated the decomposition of ABRL, significantly higher dissolved organic C (DOC), microbial biomass C (MBC), and absolute hydrolase activities were found in the ABRL treatment than in the control. These results supports that labile C inputs stimulating microbial growth, enzyme activities and cause positive PE via co-metabolic. At the later stage (LS: after 180 days), the release of structural C compounds dominated the decomposition of ABRL, a significantly lower available nitrogen (N) and a significantly higher specific potential N-acquisition (Nacq) enzymes were found in the ABRL treatment than in the control. These results suggests that microbes utilizing the C as energy to increase Nacq enzymes to decompose SOC for N mining under N limitation induced positive PE. Warming significantly increased the PEs at both stages. At the ES, warming increased the MBC at the cost of DOC, suggesting that warming intensifies the microbial co-metabolism. At the LS, warming significantly decreased the available N and increases the absolute potential oxidases activities, suggesting an increased N limitation and oxidation for N-rich recalcitrant SOC, i.e., a promoted microbial N mining. Nevertheless, we did not observe a significant effect of ABRL addition on the temperature sensitivity of SOC decomposition compared to the control. This study provides a valuable insight that warming could consistently increase the ABRL induced PE but through different microbial mechanisms along with the decomposition processing.

中文翻译：

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吸收性凋落物诱导的引发效应对不同分解阶段变暖的积极响应不一致的微生物机制


新鲜碳 （C） 诱导的引发效应 （PE） 对土壤有机碳 （SOC） 分解至关重要。气候变暖可以提高吸收性根的产生和周转，进而增加吸收性根凋落物 （ABRL） 的输入。因此，迫切需要了解 ABRL 在变暖下诱导的 PE。我们进行了一项为期 210 天的实验，将 Cunninghamia lanceolata 的 ABRL 添加到 C4 土壤中，并在 19 °C 和 23 °C 下孵育。 我们发现添加 ABRL 导致整个孵化过程中 PE 呈阳性。在早期 （ES： 前 30 d），不稳定的 C 化合物在 ABRL 的分解中占主导地位，ABRL 处理中的溶解有机 C （DOC） 、微生物生物量 C （MBC） 和绝对水解酶活性显著高于对照。这些结果支持不稳定的 C 输入刺激微生物生长、酶活性并通过共代谢导致阳性 PE。在后期 （LS： 180 天后），结构 C 化合物的释放主导了 ABRL 的分解，ABRL 处理中发现有效氮 （N） 和比电位 N 获得 （Nacq） 酶显著高于对照。这些结果表明，微生物利用 C 作为能量来增加 Nacq 酶分解 SOC 以在 N 限制下进行 N 挖掘诱导了阳性 PE。变暖显著增加了两个阶段的 PE。在 ES 中，变暖以牺牲 DOC 为代价增加了 MBC，这表明变暖加剧了微生物共代谢。在 LS 处，增温显著降低了有效氮并增加了绝对潜在氧化酶活性，表明富含 N 的顽固 SOC 的氮限制和氧化增加，即促进微生物氮挖掘。 然而，与对照相比，我们没有观察到 ABRL 添加对 SOC 分解的温度敏感性有显着影响。这项研究提供了一个有价值的见解，即变暖可以持续增加 ABRL 诱导的 PE，但通过不同的微生物机制以及分解过程。