C fluxes from incubations of California upland soil with and without synthetic iron (hydr)oxide associations

There is a growing understanding that interactions with soil mineral phases contribute to the accumulation and retention of otherwise degradable organic matter in soils and sediments. However, the bioavailability of organic compounds in mineral-organic-associations, 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 at the Blodgett Forest Research Station. 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 incubated the soils at 25 deg C. This dataset comprises the added glucose C and the cumulative fluxes over 72 and 1896 hours. 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. This dataset lists the glucose additions made to soils with and without added geothite or ferrihidrite and the C respired over the timespan of the incubations.

越来越多的研究共识认为，与土壤矿物相的相互作用可促进土壤及沉积物中原本可降解有机质的积累与留存。然而，矿物-有机质复合体中有机化合物的生物可利用性，尤其是在不同环境条件下的该特性，仍未得到充分阐释。
为评估矿物结合作用与升温对易被微生物呼吸利用的有机底物——葡萄糖（glucose）——分解过程的影响，我们开展了一系列不同温度的室内培养实验，所用土壤采集自布洛杰特森林研究站（Blodgett Forest Research Station）10–20 cm、50–60 cm及80–90 cm深度的土层。
我们将¹³C标记的葡萄糖直接添加至原位土壤中，或吸附于两种结晶度与葡萄糖吸附亲和力均存在差异的合成铁（氢）氧化物（iron (hydr)oxide）相：针铁矿（goethite）与水铁矿（ferrihydrite），随后将处理后的土壤置于25 ℃下培养。
本数据集涵盖添加的葡萄糖碳量，以及培养72小时与1896小时后的累积呼吸通量。
研究结果显示：（1）相较于土壤中游离葡萄糖的分解速率，与铁（氢）氧化物矿物结合可使葡萄糖分解速率降低99.5%以上；（2）每克碳的呼吸速率未随土层深度出现显著差异，表明不同深度土层中原位碳的可降解程度相近，且在本次培养实验条件下，总碳有效性是限制呼吸作用的核心因素，而非分解者丰度不足或水分、氧气受限；（3）添加游离葡萄糖可提升所有土层的原位碳呼吸速率，其中50–60 cm土层的提升效果最为显著；（4）总体而言，有机-矿物复合体（葡萄糖与铁（氢）氧化物）的呼吸作用对温度的敏感性低于原位碳的呼吸作用；（5）添加无有机质结合的矿物会降低50–60 cm中层土壤的呼吸速率。
研究结果凸显了矿物-有机质复合体（mineral-organic associations, MOAs）在调控土壤碳向大气的碳通量以及维持土壤碳储量方面的关键作用。本数据集列出了向添加/未添加针铁矿或水铁矿的土壤中添加的葡萄糖用量，以及整个培养周期内释放的呼吸碳量。