Raza Sajjad, Irshad Annie, Margenot Andrew, Zamanian Kazem, Li Nan, Ullah Sami, Mehmood Khalid, Ajmal Khan Muhammad, Siddique Nadeem, Zhou Jianbin, Mooney Sacha J, Kurganova Irina, Zhao Xiaoning, Kuzyakov Yakov
School of Geographical Sciences, Nanjing University of Information Science & Technology, Nanjing 210044, China.
Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, United States.
Geoderma. 2024 Mar;443:116831. doi: 10.1016/j.geoderma.2024.116831.
Soils are a major player in the global carbon (C) cycle and climate change by functioning as a sink or a source of atmospheric carbon dioxide (CO). The largest terrestrial C reservoir in soils comprises two main pools: organic (SOC) and inorganic C (SIC), each having distinct fates and functions but with a large disparity in global research attention. This study quantified global soil C research trends and the proportional focus on SOC and SIC pools based on a bibliometric analysis and raise the importance of SIC pools fully underrepresented in research, applications, and modeling. Studies on soil C pools started in 1905 and has produced over 47,000 publications (>1.7 million citations). Although the global C stocks down to 2 m depth are nearly the same for SOC and SIC, the research has dominantly examined SOC (>96 % of publications and citations) with a minimal share on SIC (<4%). Approximately 40 % of the soil C research was related to climate change. Despite poor coverage and publications, the climate change-related research impact (citations per document) of SIC studies was higher than that of SOC. Mineral associated organic carbon, machine learning, soil health, and biochar were the recent top trend topics for SOC research (2020-2023), whereas digital soil mapping, soil properties, soil acidification, and calcite were recent top trend topics for SIC. SOC research was contributed by 151 countries compared to 88 for SIC. As assessed by publications, soil C research was mainly concentrated in a few countries, with only 9 countries accounting for 70 % of the research. China and the USA were the major producers (45 %), collaborators (37 %), and funders of soil C research. SIC is a long-lived soil C pool with a turnover rate (leaching and recrystallization) of more than 1000 years in natural ecosystems, but intensive agricultural practices have accelerated SIC losses, making SIC an important player in global C cycle and climate change. The lack of attention and investment towards SIC research could jeopardize the ongoing efforts to mitigate climate change impacts to meet the 1.5-2.0 °C targets under the Paris Climate Agreement of 2015. This bibliographic study calls to expand the research focus on SIC and including SIC fluxes in C budgets and models, without which the representation of the global C cycle is incomplete.
土壤在全球碳（C）循环和气候变化中扮演着重要角色，它既可以作为大气二氧化碳（CO₂）的汇，也可以作为源。土壤中最大的陆地碳库包括两个主要部分：有机碳（SOC）和无机碳（SIC），它们各自具有不同的归宿和功能，但在全球研究关注度上存在很大差异。本研究基于文献计量分析量化了全球土壤碳研究趋势以及对SOC和SIC库的比例关注，并强调了SIC库在研究、应用和建模中未得到充分体现的重要性。关于土壤碳库的研究始于1905年，已产生超过47000篇出版物（>170万次引用）。尽管全球到2米深度的碳储量中SOC和SIC几乎相同，但研究主要集中在SOC（>96%的出版物和引用），而对SIC的研究占比极小（<4%）。大约40%的土壤碳研究与气候变化有关。尽管SIC研究的覆盖范围和出版物数量较少，但其与气候变化相关的研究影响力（每篇文献的引用次数）高于SOC。矿物相关有机碳、机器学习、土壤健康和生物炭是近期SOC研究（2020 - 2023年）的热门趋势主题，而数字土壤制图、土壤性质、土壤酸化和方解石是近期SIC的热门趋势主题。参与SOC研究的有151个国家，而参与SIC研究的有88个国家。从出版物来看，土壤碳研究主要集中在少数几个国家，仅9个国家就占了70%的研究。中国和美国是土壤碳研究的主要产出国（45%）、合作国（37%）和资助国。SIC是一个长期存在的土壤碳库，在自然生态系统中的周转率（淋溶和重结晶）超过1000年，但集约化农业实践加速了SIC的流失，使SIC成为全球碳循环和气候变化中的重要因素。对SIC研究缺乏关注和投资可能会危及为实现2015年《巴黎气候协定》中1.5 - 2.0°C目标而正在进行的缓解气候变化影响的努力。这项文献研究呼吁扩大对SIC的研究重点，并将SIC通量纳入碳预算和模型中，否则全球碳循环的表述将是不完整的。
