Biosciences Division, Argonne National Laboratory, Argonne, Illinois, United States of America.
PLoS One. 2013 Oct 30;8(10):e77880. doi: 10.1371/journal.pone.0077880. eCollection 2013.
Laboratory studies show that introduction of fresh and easily decomposable organic carbon (OC) into soil-water systems can stimulate the decomposition of soil OC (SOC) via priming effects in temperate forests, shrublands, grasslands, and agro-ecosystems. However, priming effects are still not well understood in the field setting for temperate ecosystems and virtually nothing is known about priming effects (e.g., existence, frequency, and magnitude) in boreal ecosystems. In this study, a coupled dissolved OC (DOC) transport and microbial biomass dynamics model was developed to simultaneously simulate co-occurring hydrological, physical, and biological processes and their interactions in soil pore-water systems. The developed model was then used to examine the importance of priming effects in two black spruce forest soils, with and without underlying permafrost. Our simulations showed that priming effects were strongly controlled by the frequency and intensity of DOC input, with greater priming effects associated with greater DOC inputs. Sensitivity analyses indicated that priming effects were most sensitive to variations in the quality of SOC, followed by variations in microbial biomass dynamics (i.e., microbial death and maintenance respiration), highlighting the urgent need to better discern these key parameters in future experiments and to consider these dynamics in existing ecosystem models. Water movement carries DOC to deep soil layers that have high SOC stocks in boreal soils. Thus, greater priming effects were predicted for the site with favorable water movement than for the site with limited water flow, suggesting that priming effects might be accelerated for sites where permafrost degradation leads to the formation of dry thermokarst.
实验室研究表明，在温带森林、灌木地、草地和农业生态系统中，向土壤-水系统中引入新鲜且易于分解的有机碳（OC）会通过激发效应刺激土壤 OC（SOC）的分解。然而，在温带生态系统的野外环境中，激发效应仍然没有得到很好的理解，而在北方生态系统中，激发效应（例如存在、频率和幅度）几乎一无所知。在这项研究中，开发了一个耦合的溶解 OC（DOC）运移和微生物生物量动态模型，以同时模拟土壤孔隙水中同时发生的水文、物理和生物过程及其相互作用。然后，使用该模型研究了两个黑云杉森林土壤中激发效应的重要性，其中一个土壤下有永冻层，另一个没有。我们的模拟表明，激发效应受到 DOC 输入的频率和强度的强烈控制，与更大的 DOC 输入相关的激发效应更大。敏感性分析表明，激发效应对 SOC 质量的变化最敏感，其次是微生物生物量动态（即微生物死亡和维持呼吸）的变化，这突出表明在未来的实验中迫切需要更好地区分这些关键参数，并在现有的生态系统模型中考虑这些动态。水的运动将 DOC 携带到北方土壤中具有高 SOC 储量的深层土壤中。因此，与水流有限的地点相比，具有有利水运动的地点预测会产生更大的激发效应，这表明激发效应可能会在永冻土退化导致干热喀斯特形成的地点加速。
