Pyrogenic organic carbon (PyC) is a complex, heterogeneous class of thermally altered organic substrates, but its dynamics and how its behavior changes with soil depth remain poorly understood. We conducted a laboratory incubation study to investigate the interactive effects of pyrolysis temperature and soil depth on the turnover of PyC compared to its precursor wood and native SOC (NSOC). We incubated dual-labeled (¹³C and ¹⁵N) jack pine pyrogenic organic matter produced at 300 °C (PyC300), 450 °C (PyC450), and their precursor pine wood in a fine-loamy, mixed-conifer forest soil for 745 days. A mixture of surface (0–10 cm) and subsurface (50–70 cm) forest soils, with and without labeled biomass were incubated in the dark at 55% soil water field capacity and 25 °C. Total ¹³C from PyC and wood mineralized as ¹³C-CO₂ (as % of C added to soil) declined with an increase in pyrolysis temperature as follows: 54 ± 7.7% for wood, 3.1 ± 0.2% for PyC300, and 0.94 ± 0.08% for PyC450. After 2 years, soil depth interacted with pyrolysis temperature to affect C turnover, with total wood C losses significantly declining from 70.6% in surface soils to 37.5% in subsurface soil, while total losses of PyC300 and PyC450 were unaffected by differences between surface and subsurface soils. Wood induced negative priming (i.e., decreased mineralization rates) in surface soil at days 3 and 60, while PyC300 induced positive priming (i.e., increased mineralization rates) in subsurface soil at day 60. After 2 years, unlabeled NSOC losses increased from 9.2 ± 0.8% of NSOC in unamended treatments to 16.5 ± 2.6% of NSOC with PyC450 additions. Our results suggest that PyC pyrolyzed at a given temperature can mineralize at similar rates between soil depths, and high amounts of PyC450 in subsurface soils can stimulate NSOC losses. These findings indicate that soil depth imposes critical controls on PyC dynamics belowground.

热解有机碳（PyC）是一类复杂的，异质的热改变的有机底物，但人们对其动力学以及其行为随土壤深度的变化知之甚少。我们进行了一项实验室孵化研究，以研究热解温度和土壤深度与PyC与其前体木材和天然SOC（NSOC）相比的相互作用。我们将在300°C（PyC300），450°C（PyC450）和它们的前体松木中产生的双标记（¹³ C和¹⁵ N）千斤顶松热生有机物质在细粒松散的针叶林森林土壤中孵育，用于745天。在有和没有标记生物量的情况下，将表层（0–10 cm）和表层（50–70 cm）森林土壤的混合物在黑暗中于55％的土壤水田容量和25°C下孵育。全部的来自PyC的¹³ C，并且木材矿化为¹³ C-CO ₂（以添加到土壤中的C的百分比表示）随着热解温度的升高而降低，如下所示：木材为54±7.7％，PyC300为3.1±0.2％，PyC450为0.94±0.08％。2年后，土壤深度与热解温度相互影响，影响了碳的转化，木材总碳损失从表层土壤的70.6％显着下降到表层土壤的37.5％，而PyC300和PyC450的总损失不受表层和表层下差异的影响。土壤。木材在第3天和第60天诱导了表层土壤的负引发（即降低的矿化率），而PyC300在第60天引起了表层土壤中的正引发（即，增加了矿化率）。2年后，未标记的NSOC损失从9.2±增加未经修饰的治疗的NSOC为0.8％，添加PyC450的则为NSOC的16.5±2.6％。我们的结果表明，在给定温度下热解的PyC可以在土壤深度之间以相似的速率矿化，并且地下土壤中的大量PyC450可以刺激NSOC损失。这些发现表明，土壤深度对地下PyC动力学具有重要控制作用。