Responses of soil organic carbon decomposition to warming depend on the natural warming gradient
Responses of soil organic carbon decomposition to warming depend on the natural warming gradient
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DOI：
10.1016/j.geoderma.2019.02.017
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发表时间：
2019-06
期刊：
影响因子：
6.1
通讯作者：
Wenfang Xu;W. Yuan;Lilun Cui;Minna Ma;Fen-Guo Zhang
中科院分区：
文献类型：
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作者：
Wenfang Xu;W. Yuan;Lilun Cui;Minna Ma;Fen-Guo Zhang
土壤有机碳（SOC）分解对气候变暖的响应不一致。响应随实验变暖的持续时间而变化;然而，即使是最长的变暖实验也不能解释未来可能的气候驱动的SOC分解变化。本文研究了青藏高原两个海拔高度（低海拔，暖点;高海拔，凉点）土壤（0 - 10、10 - 20和20 - 30 cm土层）SOC分解对自然升温的响应。我们将这些土壤样品在三个温度下孵育（即，5、10和15 ° C），并分析了CO2排放速率，以评估SOC分解对变暖的响应。结果表明，低海拔（暖点）土壤表层（0 - 10 cm和10 - 20 cm）CO2排放速率高于高海拔（凉点）土壤。相比之下，底土（20 - 30厘米）样本显示较高的CO2排放率在较高的海拔点。土壤微生物生物量碳（MBC）在表层和下层表现出相似的变化规律，表明土壤微生物生物量碳对有机碳的分解具有调节作用。总体而言，亚表层土壤CO2排放速率较高，这可能是由于亚表层土壤中碳的脆弱性较高以及微生物碳利用效率降低的结果。对于所有采样点，在5 ° C培养温度下观察到最大的CO2排放率和MBC增加，表明耐寒微生物可能经历适应，使其能够耐受寒冷条件。综上所述，我们的研究结果提供了证据的自然变暖梯度使用气候序列的方法来说明微生物调解在控制SOC分解的重要性。此外，在预测碳-气候反馈时，模型应考虑表土和底土土壤碳动态的不同机制。
Inconsistent responses of soil organic carbon (SOC) decomposition to climate warming have been observed in field experiments. Responses vary with the duration of experimental warming; however, even the longest warming experiment could not account for possible future climate-driven changes in SOC decomposition. Here, we investigated the responses of SOC decomposition to natural warming in soil samples (at soil depths of 0–10, 10–20, and 20–30 cm) collected at two altitudes (lower-elevation, warm points; higher-elevation, cool points) with an approximate 1 °C difference in mean soil temperature, representing an infinite natural warming duration in the Qinghai–Tibetan Plateau. We incubated these soil samples at three temperatures (i.e., 5, 10, and 15 °C) and analyzed the CO2emission rate to assess the responses of SOC decomposition to warming. The results revealed higher CO2emission rates from topsoil (0–10 and 10–20 cm) samples collected at lower-elevation (warm points) than higher-elevation (cool points). By contrast, subsoil (20–30 cm) samples showed higher CO2emission rates at higher-elevation points. Soil microbial biomass carbon (MBC) exhibited similar patterns in topsoil and subsoil, indicative of the regulation SOC decomposition by MBC. Overall, CO2emission rates were higher in subsoil, possible the result of the high vulnerability of carbon and decreased microbial carbon use efficiency in subsoil. For all sampling points, the largest CO2emission rates and MBC increases were observed at 5 °C incubation temperature, demonstrating that cold-tolerant microbes may undergo adaptations that enable their tolerance to cold conditions. Taken together, our findings provide evidence of the natural warming gradient using a climosequence approach to illustrate the importance of microbial-mediation in controlling SOC decomposition. Moreover, models should consider different mechanisms of soil carbon dynamics in topsoil and subsoil when predicting carbon–climate feedback.