NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management, Forest Research Institute, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, QC, Canada.
Canadian Forest Service, Laurentian Forestry Centre, Natural Resources Canada, Québec, QC, Canada.
Glob Chang Biol. 2018 Oct;24(10):4797-4815. doi: 10.1111/gcb.14365. Epub 2018 Jul 16.
The accumulation of soil carbon (C) is regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the main drivers of soil C accumulation in the boreal forest of eastern North America. Ecosystem C pools were measured in 72 sites of fire origin that burned 2-314 years ago over a vast region with a range of ∆ mean annual temperature of 3°C and one of ∆ 500 mm total precipitation. We used a set of multivariate a priori causal hypotheses to test the influence of time since fire (TSF), climate, soil physico-chemistry and bryophyte dominance on forest soil organic C accumulation. Integrating the direct and indirect effects among abiotic and biotic variables explained as much as 50% of the full model variability. The main direct drivers of soil C stocks were: TSF >bryophyte dominance of the FH layer and metal oxide content >pH of the mineral soil. Only climate parameters related to water availability contributed significantly to explaining soil C stock variation. Importantly, climate was found to affect FH layer and mineral soil C stocks indirectly through its effects on bryophyte dominance and organo-metal complexation, respectively. Soil texture had no influence on soil C stocks. Soil C stocks increased both in the FH layer and mineral soil with TSF and this effect was linked to a decrease in pH with TSF in mineral soil. TSF thus appears to be an important factor of soil development and of C sequestration in mineral soil through its influence on soil chemistry. Overall, this work highlights that integrating the complex interplay between the main drivers of soil C stocks into mechanistic models of C dynamics could improve our ability to assess C stocks and better anticipate the response of the boreal forest to global change.
土壤碳（C）的积累受到非生物和生物因素之间复杂相互作用的调节。我们的研究旨在确定东北北美北方森林土壤 C 积累的主要驱动因素。在一个具有 3°C 的平均年温差和 500mm 的总降水量差异的广阔地区，对 72 个火灾起源的生态系统 C 池进行了测量，这些火灾发生在 2-314 年前。我们使用了一套多变量先验因果假设来测试火后时间（TSF）、气候、土壤物理化学和苔藓优势对森林土壤有机 C 积累的影响。整合非生物和生物变量之间的直接和间接影响，解释了高达 50%的全模型变异性。土壤 C 储量的主要直接驱动因素是：TSF >藓层优势和金属氧化物含量 >矿质土壤 pH。只有与水分可用性相关的气候参数对解释土壤 C 储量变化有显著贡献。重要的是，气候通过对藓层和矿物土壤中 C 储量的影响，分别通过对苔藓优势和有机金属络合的影响，间接影响 FH 层和矿物土壤 C 储量。土壤质地对土壤 C 储量没有影响。随着 TSF 的增加，FH 层和矿物土壤中的土壤 C 储量都有所增加，这一效应与矿物土壤中 pH 值随 TSF 降低有关。因此，TSF 似乎是土壤发育和矿物土壤中 C 固存的重要因素，因为它影响土壤化学。总的来说，这项工作强调了将土壤 C 储量的主要驱动因素之间的复杂相互作用整合到 C 动态的机制模型中，可以提高我们评估 C 储量的能力，并更好地预测北方森林对全球变化的响应。
