Data for "Soil carbon dynamics during drying vs. rewetting: Importance of antecedent moisture conditions"

This dataset contains data used for the paper "Soil carbon dynamics during drying vs. rewetting: importance of antecedent moisture conditions". The Related References field will be updated with a full citation when available. Soil moisture influences soil carbon dynamics, including microbial growth and respiration. The response of such ‘soil respiration’ to moisture changes is generally assumed to be linear and reversible, i.e. to depend only on the current moisture state. Current models thus do not account for antecedent soil moisture conditions when determining soil respiration or the available substrate pool. We conducted a laboratory incubation to determine how the antecedent conditions of drought and flood influenced soil organic matter (SOM) chemistry, bioavailability, and respiration. We sampled soils from an upland coastal forest, Beaver Creek, WA USA, and subjected them to drying and rewetting treatments. For the drying treatment, field moist soils were saturated and then dried to 75, 50, 35, and 5 % saturation. In the rewetting treatment, field moist soils were air-dried and then rewet to 35, 50, 75, and 100 % saturation. We measured respiration and water extractable organic carbon (WEOC) concentrations and used 1H-NMR and FT-ICR-MS to characterize the WEOC pool across the treatments. The drying vs. wetting treatment strongly influenced SOM bioavailability, as rewet soils (with antecedent drought) had greater WEOC concentrations and respiration fluxes compared to the drying soils (with antecedent flood). In addition, air-dry soils had the highest WEOC concentrations, and the NMR-resolved peaks showed a strong contribution of protein groups in these soils. Both NMR and FT-ICR-MS analyses indicated increased contribution of complex aromatic groups/molecules in the rewet soils, compared to the drying soils. We suggest that drying introduced organic matter into the WEOC pool via desorption of aromatic molecules and/or by microbial cell lysis, and this stimulated microbial mineralization rates. Our work indicates that even short-term shifts in antecedent moisture conditions can strongly influence soil C dynamics at the core scale. The predictive uncertainties in current soil models may be reduced by a more accurate representation of soil water and C persistence that includes a mechanistic and quantitative understanding of the impact of antecedent moisture conditions. This dataset contains a compressed (.zip) archive of the data and R scripts used for this manuscript. The dataset includes files in .csv and .txt format, which can be accessed and processed using MS Excel or R. NMR data are provided as raw output data (accessed in Bruker TopSpin or MestreNova) as well as the MestreNova-processed files. This archive can also be accessed on GitHub at https://github.com/kaizadp/hysteresis_and_soil_carbon (DOI: 10.5281/zenodo.4432885).本数据集用于支撑论文《干湿循环下的土壤碳动态：前期水分条件的重要性》（原标题：Soil carbon dynamics during drying vs. rewetting: importance of antecedent moisture conditions）。 相关参考文献字段将在获取完整引用信息后进行更新。 土壤水分会调控土壤碳动态过程，包括微生物生长与呼吸作用。现有研究普遍认为，此类"土壤呼吸"对水分变化的响应呈线性且可逆，即仅取决于当前的水分状态。因此，当前的土壤碳循环模型在计算土壤呼吸或有效底物库时，并未考虑前期土壤水分条件的影响。 我们开展了室内培养实验，以探明干旱与淹水的前期水分条件如何影响土壤有机质（SOM）的化学特征、生物可利用性及呼吸作用。我们从美国华盛顿州比弗溪（Beaver Creek）的一处高地沿海森林采集土壤样品，并对其开展干湿循环处理。在干燥处理组中，我们将野外原状湿润土壤饱和后，分别干燥至饱和含水量的75%、50%、35%与5%；在复水处理组中，我们将野外原状湿润土壤风干后，分别复水至饱和含水量的35%、50%、75%与100%。 我们测定了土壤呼吸速率与水溶性有机碳（WEOC）浓度，并借助1H-NMR与FT-ICR-MS对各处理组的WEOC库进行了表征。干燥与复水处理对SOM的生物可利用性产生了显著影响：复水组土壤（前期经历干旱）的WEOC浓度与呼吸通量均高于干燥组土壤（前期经历淹水）。此外，风干土壤的WEOC浓度最高，且核磁共振波谱解析的峰图显示，此类土壤中蛋白质基团占比极高。 核磁共振波谱与傅里叶变换离子回旋共振质谱分析均表明，相较于干燥组土壤，复水组土壤中复杂芳香族基团/分子的占比有所提升。我们推测，干燥过程通过芳香族分子的解吸附作用或微生物细胞裂解，将有机质释放至WEOC库中，进而提升了微生物的矿化速率。 本研究表明，即便只是短期的前期水分条件变化，也会在核心尺度上对土壤碳动态产生显著影响。若能基于对前期水分条件影响的机制性与定量化理解，更精准地表征土壤水分与碳固持过程，则可降低当前土壤模型的预测不确定性。 本数据集包含本论文所用数据与R脚本的压缩归档文件（.zip格式）。数据集内包含.csv与.txt格式的文件，可通过MS Excel或R语言进行读取与处理。核磁共振波谱数据同时提供了原始输出文件（可通过Bruker TopSpin或MestreNova软件读取）以及经MestreNova处理后的文件。该归档文件也可通过以下GitHub链接获取：https://github.com/kaizadp/hysteresis_and_soil_carbon（DOI: 10.5281/zenodo.4432885）。