Hicks Pries, Sulman, et al 2018. In situ incubation of 13C-labeled litter in three soil pits at Blodgett Forest, CA from 2013 to 2016

Even though over half of the world's soil organic carbon (SOC) is stored in subsoils (>20 cm deep), and the old ages of subsoil OC indicate its cycling differs from surface SOC, there are few studies examining in situ decomposition processes in deep soils. The purpose of this dataset is to elucidate these processes. In this study we added 13C-labeled fine roots to 15, 55, and 95 cm depths of a well-characterized coniferous forest Alfisol and monitored the amount of root-derived C remaining over 6, 12, and 30 months. We recovered the root-derived C in microbial phospholipid fatty acids (PLFAs) after 6 months and in coarse (>2 mm) particulate, fine (<2 mm) particulate, and dense, mineral-associated pools after 6, 12, and 30 months. Overall, root decomposition in the first 6 months was similar among all depths but significantly diverged at 30 months with faster decomposition at 15 cm than at 95 cm. There were more fungal and Gram negative-associated PLFAs at 15 cm than at 95 cm, and 13C analysis revealed those microbial groups preferred the added root carbon to native SOC. Mineral-associations were not the cause of slower decomposition at depth because similar amounts of applied root C was recovered in the dense fraction at all depths. The largest difference among depths was in the amount of root C recovered in the coarse particulate fraction, which was greater at 95 cm (50%) than at 15 cm (15%). Slower decomposition of the particulate pool at depth likely contributed to the increase in C:N ratios and depletion of δ13C values below 60 cm depth in our soil profiles. Simulations of these soils using the CORPSE model, which incorporates microbial priming effects and mineral stabilization of SOC, reproduced patterns of particulate and mineral-associated SOC over both time and depth and suggested that a lack of priming by root exudates at depth could account for the slower decomposition rate of particulate root material. Decomposition of deep particulate SOC may increase if root exudation or dissolved OC transport to depth increases.This dataset includes (1) characterization of the soil pits prior to litter addition, (2) characterization of how the litter changed after 6, 12, and 30 months, and (3) the CORPSE model structure, parameterization, and output.

尽管全球超过一半的土壤有机碳（SOC）储存在亚表层土壤（深度>20厘米）中，且亚表层有机碳的周转周期与表层土壤有机碳存在显著差异，但针对深层土壤原位分解过程的研究仍相对匮乏。
本数据集旨在阐明此类深层土壤的原位分解过程。
本研究将13C标记细根施加于特征明确的针叶林淋溶土（Alfisol）的15、55和95厘米深度处，并在6、12和30个月内监测根源碳的残留量。在培养6个月后，我们测定了微生物磷脂脂肪酸（PLFA）中的根源碳含量；在6、12和30个月时，分别测定了粗颗粒（>2毫米）、细颗粒（<2毫米）以及致密矿物结合态组分中的根源碳含量。
整体而言，前6个月的细根分解速率在各深度间无显著差异，但在30个月时出现显著分化：15厘米深度处的分解速率显著快于95厘米深度处。15厘米深度处的真菌与革兰氏阴性菌相关磷脂脂肪酸含量高于95厘米深度处，且13C标记分析显示，相较于原生土壤有机碳，这些微生物类群更偏好利用添加的根源碳。
矿物结合作用并非导致深层土壤分解速率减缓的原因，因为各深度的致密组分中回收的施加根源碳量并无显著差异。各深度间最大的差异体现在粗颗粒组分中回收的根源碳占比：95厘米深度处的占比（50%）显著高于15厘米深度处（15%）。
深层颗粒态组分的分解速率较慢，可能导致了本研究土壤剖面中60厘米以下土层的碳氮比升高以及δ13C值耗竭。
本研究采用CORPSE模型（该模型整合了微生物激发效应与土壤有机碳的矿物稳定化过程）对这些土壤进行模拟，结果重现了不同时间与深度下颗粒态与矿物结合态土壤有机碳的变化模式，且表明深层缺乏根分泌物引发的激发效应，可能是颗粒态根源碳分解速率较慢的原因。
若深层土壤的根分泌物输入或溶解态有机碳（dissolved OC）向下输送量增加，深层颗粒态土壤有机碳的分解速率可能会提升。
本数据集包含以下三部分内容：（1）添加凋落物前的土壤剖面特征表征数据；（2）6、12和30个月后凋落物的变化特征数据；（3）CORPSE模型的结构、参数化方案与模拟输出结果。