Soils are a globally important reservoir of organic carbon. There is a growing understanding that interactions with soil mineral phases contribute to the accumulation and retention of otherwise degradable organic matter (OM) in soils and sediments. However, the bioavailability of organic compounds in mineral-organic-associations (MOAs), especially under varying environmental conditions is not well known. To assess the impact of mineral association and warming on the decomposition of an easily respirable organic substrate (glucose), we conducted a series of laboratory incubations at different temperatures with field-collected soils from 10 to 20 cm, 50–60 cm, and 80–90 cm depth. We added ¹³C-labeled glucose either directly to native soil or sorbed to one of two synthetic iron (hydr)oxide phases (goethite and ferrihydrite) that differ in crystallinity and affinity for sorbing glucose. We found that: (1) association with the Fe (hydr)oxide minerals reduced the decomposition rate of glucose by > 99.5% relative to rate of decomposition for free glucose in soil; (2) the respiration rate per gram carbon did not differ appreciably with depth, suggesting a similar degree of decomposability for native C across depths and that under the incubation conditions total carbon availability represents the principal limitation on respiration under these conditions as opposed to reduced abundance of decomposers or moisture and oxygen limitations; (3) addition of free glucose enhanced native carbon respiration at all soil depths with the largest effect at 50–60 cm; (4) in general respiration of the organo-mineral complex (glucose and iron-(hydr)oxide) was less temperature sensitive than was respiration of native carbon; (5) the addition of organic free mineral decreased the rate of soil respiration in the intermediate 50–60 cm depth soil. The results emphasize the key role of MOAs in regulating the fluxes of carbon from soils to the atmosphere and in turn the stocks of soil carbon.

中文翻译：

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地下土壤中的合成（铁）氧化物-葡萄糖缔合：对矿物缔合碳分解性的影响

土壤是全球重要的有机碳库。人们日益认识到，与土壤矿物相的相互作用有助于土壤和沉积物中原本可降解的有机物（OM）的积累和保留。但是，有机化合物在矿物-有机缔合（MOA）中的生物利用度，特别是在变化的环境条件下，尚未广为人知。为了评估矿物缔合和变暖对易呼吸的有机底物（葡萄糖）分解的影响，我们在田间收集的10至20 cm，50-60 cm和80的土壤上，在不同温度下进行了一系列实验室培养–90厘米深。我们加了¹³C标记的葡萄糖直接进入天然土壤，或吸附到结晶度和吸附葡萄糖亲和力不同的两个合成铁（氢）氧化物相（针铁矿和水铁矿）之一。我们发现：（1）与氢氧化铁矿物质的结合使葡萄糖的分解速率相对于土壤中游离葡萄糖的分解速率降低了> 99.5％；（2）每克碳的呼吸速率随深度变化不明显，表明不同深度的天然C的分解度相似，并且在孵化条件下，总碳利用率代表了在这些条件下对呼吸的主要限制，而不是丰度降低。分解物或水分和氧气的限制；（3）添加游离葡萄糖可增强所有土壤深度的天然碳呼吸，在50-60 cm处效果最大；（4）一般而言，有机矿物质复合物（葡萄糖和氧化铁（氢）氧化物）的呼吸对温度的敏感性低于对天然碳的呼吸。（5）添加有机游离矿物质会降低中等深度50–60 cm土壤的土壤呼吸速率。结果强调了MOA在调节碳从土壤到大气中的通量以及土壤碳储量中的关键作用。