Abstract. The temperate region of Western Europe underwent dramatic climatic and environmental change during the last deglaciation. Much of what is known about the terrestrial ecosystem response to deglacial warming stems from pollen preserved in sediment sequences, providing information on vegetation composition. Other ecosystem processes, such as soil respiration, remain poorly constrained over past climatic transitions, but are critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Here we show that speleothem carbon isotope (δ¹³C_spel) records may retain information on local soil respiration, and allow its reconstruction over time. While this notion has been proposed in the past, our study is the first to rigorously test it, using a combination of multi-proxy geochemical analysis (δ¹³C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (using the radiocarbon reservoir effect) from the δ¹³C_spel signal to derive changes in respired δ¹³C. Coupling of soil gas pCO₂ and δ¹³C via a mixing line describing diffusive gas transport between an atmospheric and a respired end member allows modelling of changes in soil respiration in response to temperature. Using this coupling and a range of other parameters describing carbonate dissolution and cave atmospheric conditions, we generate large simulation ensembles from which the results most closely matching the measured speleothem data are selected. Our results robustly show that an increase in soil pCO₂ (and thus respiration) is needed to explain the observed deglacial trend in δ¹³C_spel. However, the Q₁₀ (temperature sensitivity) derived from the model results is higher than current measurements, suggesting that part of the signal may be related to a change in the composition of the soil respired δ¹³C, likely from changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.

中文翻译：

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石笋碳同位素表明在西欧，温度变化导致土壤呼吸作用增加

摘要。在最后一次冰消期间，西欧的温带地区经历了剧烈的气候和环境变化。关于陆地生态系统对冰河变暖的反应的大部分已知信息都来自沉积在沉积物中的花粉，从而提供了有关植被组成的信息。在过去的气候转变过程中，其他生态系统过程（如土壤呼吸）的约束仍然很有限，但对于了解全球碳循环及其对持续的人为变暖的响应至关重要。在这里，我们表明，钟乳石碳同位素（δ ¹³ C ^ _SPEL）记录可以保留有关当地土壤呼吸的信息，并允许其随时间重建。虽然这个概念在过去被提出，我们的研究是第一次严格的测试，使用多代理地球化学分析相结合（δ ¹³ C，钙同位素和放射性碳）从西班牙北三环洞穴堆积物，并定量前进对土壤，岩溶和洞穴的过程进行建模。我们的研究是第一量化和除去之前方解石沉淀的效果（PCP，使用Ca同位素）和基岩溶解（使用放射性碳储作用）从δ ¹³ Ç _SPEL在呼出δ信号以导出变化¹³的耦合C.土壤气体的pCO ₂和δ ¹³通过描述大气和呼吸端构件之间扩散气体传输的混合线的C，可以模拟土壤呼吸响应温度的变化。使用这种耦合以及描述碳酸盐溶解和洞穴大气条件的一系列其他参数，我们生成了大型模拟集合，从中选择了与实测鞘脂数据最接近的结果。我们的结果有力表明，在土壤的pCO增加₂（并且因此呼吸）是需要解释δ所观察到的趋势冰消¹³ Ç _SPEL。但是，Q ₁₀（温度敏感性）从模型结果导出比电流测量更高，这表明信号的一部分可能与在土壤中的呼出δ组成变化¹³ ℃，有可能从改变衬底通过从植被的生物量的贡献日益增加的全新世的开始。