Upland soils constitute the second largest and the only manageable methane (CH) sink, yet current estimations remain substantially uncertain. This review identifies the primary sources of model uncertainties and emphasize the need for improved model accuracy and necessary comprehensiveness to better estimate upland soil CHuptake under global change. We highlight that the limitations of diffusion-reaction models include oversimplified assumptions of upland soils as constant CHsinks and insufficient parameterization of the microbial CH oxidation constants. In process-based biogeochemical models, uncertainties stem from the omission of soil O status and oversimplified Michaelis–Menten kinetics parameterization for upland soils. We also provide three suggestions for better addressing the spatiotemporal variations in soil CH uptake globally. 1) Accounting for the balance between methanotrophy and methanogenesis is the key to accurately assessing CH fluxes at fine to large scales. 2) Improved response curves of methanotrophy to soil moisture, temperature, and mineral nitrogen, as the most important regulators, are needed to correct the underestimated spatial variations in the size of the soil CH sink globally. 3) Improving parameterizations based on the relationships between environmental factors and methanotrophic communities is necessary. Our synthesized model estimations and field observations reveal that inconsistent estimations of the spatial variations in forest soil CH sinks, and the neglect of the drylands (arid and semiarid ecosystems) CH sink are the major sources of uncertainty for global upland soil CH sinks. Given the great potential of soil CH uptake in mitigating the imbalanced global CH budget, we emphasize the necessity of addressing the soil CH exchanges in these key ecosystems, particularly under the impacts of global changes, by integrating continuous in-situ observations with improved models to fully account for the dynamics of the terrestrial CH sink. This review contributes to a more accurate estimation, management, and optimization of global upland soil CH sinks, aiding in the development of effective climate change mitigation strategies.

中文翻译：

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全球高地土壤甲烷汇的量化和不确定性：过程、控制、模型限制和改进

高地土壤是第二大也是唯一可管理的甲烷（CH）汇，但目前的估计仍然存在很大的不确定性。本综述确定了模型不确定性的主要来源，并强调需要提高模型的准确性和必要的全面性，以更好地估计全球变化下的高地土壤 CH 吸收量。我们强调扩散反应模型的局限性包括将高地土壤假设为恒定的 CH 汇以及微生物 CH 氧化常数的参数化不足。在基于过程的生物地球化学模型中，不确定性源于土壤氧状态的遗漏和高地土壤米氏动力学参数化的过度简化。我们还提供了三项建议，以更好地解决全球土壤 CH 吸收的时空变化。 1) 考虑甲烷氧化和产甲烷作用之间的平衡是从精细到大规模准确评估 CH 通量的关键。 2）需要改进甲烷氧化菌对土壤湿度、温度和矿质氮（作为最重要的调节因子）的响应曲线，以纠正全球土壤甲烷汇规模被低估的空间变化。 3）有必要根据环境因素与甲烷氧化菌群落之间的关系改进参数化。我们的综合模型估计和实地观测表明，对森林土壤CH汇空间变化的不一致估计以及对旱地（干旱和半干旱生态系统）CH汇的忽视是全球高地土壤CH汇不确定性的主要来源。鉴于土壤 CH 吸收在缓解全球 CH 预算失衡方面的巨大潜力，我们强调有必要解决这些关键生态系统中的土壤 CH 交换问题，特别是在全球变化的影响下，通过将连续的原位观测与改进的模型相结合，充分考虑了陆地CH汇的动态。本次审查有助于更准确地估计、管理和优化全球高地土壤甲烷汇，有助于制定有效的气候变化缓解战略。