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Review

Soil Organic Carbon Research and Hotspot Analysis Based on Web of Science: A Bibliometric Analysis in CiteSpace

by
Manman Fan
1,
Wenyan Yang
1,
Jingtao Wu
1,*,
Huan Zhang
2,
Zhengwei Ye
1 and
Muhammad Shaukat
3
1
School of Geography and Planning, Huaiyin Normal University, Huaian 223300, China
2
College of Marine Science and Engineering, Nanjing Normal University, Nanjing 210023, China
3
Department of Agricultural Sciences, Allama Iqbal Open University, Islamabad 44000, Pakistan
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(10), 1774; https://doi.org/10.3390/agriculture14101774
Submission received: 25 August 2024 / Revised: 3 October 2024 / Accepted: 6 October 2024 / Published: 9 October 2024
(This article belongs to the Section Agricultural Soils)
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Abstract

:
Soil carbon sequestration is an important process of the terrestrial carbon cycle, and even slight changes in soil carbon will trigger drastic variations in the global carbon pool. In this study, we used the CiteSpace software to analyze the development of research on soil organic carbon (SOC) and its current status from various perspectives, with the goal of revealing research hotspots and trends of SOC. A total of 3909 studies published between 2014 and 2023 were included in the analysis. Results show that China and the USA lead with a significant number of publications on SOC, which underscores their considerable interest in the subject. France and the USA exhibit a very high international influence in this field, with their intermediary centrality reaching up to 0.3 and 0.21, respectively. Among institutions, the Chinese Academy of Sciences is the largest contributor in terms of the number of publications, with a high centrality of 0.09, indicating this institution has built close collaboration and significant influence in this field. Kuzyakov Yakov achieved the highest publication record, with Lal Rattan sharing the second position. The hotspots in SOC can be summarized into the following aspects: conservation tillage, carbon sequestration, microbial biomass, and driving forces. The research focus has gradually shifted from macroscopic trends to explanations based on micro-level biological dynamics. Driving forces such as soil type, land use, and environmental conditions have a significant impact on the quantity, turnover, and spatiotemporal distribution of SOC. We highlighted that more attention should be paid to the mechanism of SOC transformation and stabilization, which is essential for developing more precise models of carbon cycling in the soil and for formulating effective strategies to maintain sustainable agriculture and mitigate climate change.

1. Introduction

Global warming has emerged as a profound challenge to humanity, prompting an urgent need to mitigate the rise in atmospheric carbon dioxide (CO2) concentrations [1]. Soil plays a crucial role in the global carbon cycle, with soil organic carbon (SOC) accounting for two-thirds of the terrestrial ecosystem carbon reservoir [2,3]. The dynamics of SOC accumulation and decomposition significantly influence global climate change and serve as critical indicators of soil fertility and quality [4,5,6,7,8]. A great number of articles on SOC have been published all over the world, and the past decade has witnessed a significant rise in this field in the number of publications. As global climate change becomes increasingly severe, people recognize the significance of understanding and addressing soil carbon sequestration, which could be helpful for reducing carbon emissions and mitigating global warming [9,10,11,12,13]. It is speculated that research on SOC will continue to emerge as a hot topic in the field of environmental science in the coming years.
The carbon reservoir in soil is composed of both organic and inorganic carbon [14]. Soil organic carbon, derived from humus, plant and animal residues, and microbial biomass, is accumulated through biological carbon fixation processes and is characterized by a relatively short turnover period [15]. In contrast, soil inorganic carbon is the result of a slow and gradual accumulation over geological time, largely controlled by abiotic processes [16]. Therefore, research on soil carbon sequestration predominantly focuses on SOC. During the process of soil carbon sequestration, terms such as soil aggregates and microbial biomass have been of wide concern [17,18,19,20]. Soil aggregates are the essential components of soil and the minimum unit of soil structure. It has been documented that approximately 90% of SOC is sequestered within soil aggregates in the surface layer [21]. Therefore, its formation process is closely related to soil carbon sequestration. The formation of soil aggregates is the result of the interplay between biological, abiotic, and environmental factors [22]. There exists a symbiotic relationship between soil aggregates and soil microorganisms. On one hand, soil aggregates provide a nurturing environment that serves as a habitat for microorganisms; on the other hand, these microorganisms play a pivotal role as a biotic factor in the aggregation process of soil [23,24]. Studies have revealed that the disruption of soil aggregates would accelerate the decomposition of SOC and result in a reduction of soil carbon [25]. Barreto et al. [26] reported that after the disruption of forest soil aggregates larger than 8 mm, between 2 mm and 8 mm, and between 0.25 mm and 2.00 mm, the mineralization rate of SOC was 878%, 300%, and 345% higher, respectively.
The fluxes of SOC are intricately balanced between sources and sinks [27,28,29]. The input of exogenous organic matter leads to SOC accumulation [30,31], while processes such as soil respiration and leaching result in carbon loss [32,33,34]. Multiple factors, including soil properties (pH, texture, moisture, etc.), climate (temperature, precipitation, etc.), topography (elevation, slope, aspect, etc.), vegetation (vegetation type, coverage, etc.), and anthropogenic factors (such as straw return, tillage, fertilization, etc.), can modulate the balance between SOC decomposition and accumulation [35,36,37,38,39]. These factors, in turn, influence the emission of CO2 to the atmosphere, affecting global climate change and exerting profound implications for the distribution, composition, and functioning of terrestrial ecosystems [15]. For example, Le Noë et al. [40] studied the carbon dynamics of agricultural soils in France from 2004 to 2014 and revealed a “carbon sink” effect under current management practices. Vitharana et al. [41] estimated the SOC stocks of surface 0–30 cm and subsurface 30–100 cm Sri Lankan soils based on 122 soil profiles, summarizing that the combination of soil data with appropriate environmental covariates and pedogenic information will be helpful in improving the accuracy of estimating SOC stocks. Zhang et al. [42] explored the interactive effects of temperature and precipitation on the SOC of dryland in East China, highlighting significant differences among different soil types. There are many scholars focusing on the effects of conservation tillage on SOC dynamics. Among them, Martín et al. [43] reported a 15% increase in soil carbon sequestration in Majorca, Spain, from 2006 to 2017, emphasizing the importance of adopting conservation agricultural practices such as crop rotation or reduced tillage techniques. Wei et al. [44] simulated the dynamics of SOC in Northeast China by the CENTURY model, indicating an increasing carbon sequestration rate under a no-till scenario. In fact, conservation tillage is related with residue mulch, cover crop, crop rotation, reduced tillage, or no tillage and integrated nutrient management, etc. [45,46,47,48]. The purpose of conservation tillage or conservation agriculture is to efficiently enhance carbon sequestration, build resilience and mitigation against climate change, and achieve sustainable agricultural development [49], while traditional ploughing tillage involves extensive exposure of soil, breaking up aggregates and thus making SOC more susceptible to microbial decomposition. In contrast, no-tillage practices cause less disruption to soil structure and preserve the stability of soil aggregates, which will slow down the decomposition of SOC and reduce the leaching of carbon from agricultural soils [45,50]. Although numerous studies have been carried out on soil carbon sequestration and influencing factors, it is still unclear how SOC varies under different environmental conditions and how to effectively reduce carbon losses from soil.
Bibliometrics, a statistical and quantitative method used to analyze the literature, explores the distribution, structure, characteristics, and linkage in a field [51]. CiteSpace, a prevalent bibliometric tool, is widely used for visualizing keyword co-occurrences and constructing knowledge maps of literature, facilitating scientific statistics and data mining across various fields [52]. The Web of Science Core Collection (WOSCC) is one of the most comprehensive academic databases in the world [53]. In this study, we investigated the research on SOC using data collected from the WOSCC from 2014 to 2023. The bibliometric analysis by CiteSpace was conducted to study the evolution of publication numbers, collaboration networks, keyword co-occurrences and co-citations. The results of this analysis can reveal the evolution, hotspots, and potential trends in this field, which will provide valuable insights for future research endeavors.

2. Materials and Methods

2.1. Data Sources

All datasets used in this study were obtained from the WOSCC database on 6 January 2024. The selected database contains comprehensive indexing records of the majority of high-quality articles from multiple disciplines. It boasts the longest time span and the most complete collection of documents, ensuring the accuracy and reliability of the bibliometric analysis [51]. The search criteria was “Subject: (soil organic carbon)”. The retrieval time span was set from 1 January 2014 to 31 December 2023. After eliminating duplicates, 3909 articles were finally selected for the bibliometric analysis. Data were downloaded in the format of “full records and cited references” and saved as plain text files as data samples for analysis. The output file was renamed as “download_*.txt”.

2.2. Data Analysis

CiteSpace is a Java-based visualization tool designed by Dr. Chaomei Chen, which provides a comprehensive visual analysis and help researchers to identify trends, patterns, and influential works in their fields [51]. It primarily operates on the theories of co-citation analysis and pathFinder network algorithms to measure specific fields of literature, thereby identifying key pathways and knowledge turning points in the evolution of academic disciplines. CiteSpace facilitates the creation of scientific knowledge maps to analyze the underlying dynamics of disciplinary development and to detect emerging trends within the field. The software is capable of generating collaboration maps for literature, highlighting author, national, and institutional collaborations, as well as co-occurrence maps that illustrate the interplay of characteristic terms, keywords, and subject categories [54,55]. Additionally, it provides co-citation maps for cited documents, authors, and journals, offering a comprehensive visual representation of the scholarly landscape [56].
In this study, CiteSpace 6.2 R7 and 6.3.R3 software were used to explore the publications and cooperation networks, the evolution and trends of research on SOC. The time slice was set to one year. By setting the node type in CiteSpace to “country”, “author”, “institution”, and “keyword”, respectively, we obtained the research overview and dynamics of SOC in the terrestrial ecosystem.

3. Results

3.1. Analysis of Annual Publications

The number of academic publications and their temporal distribution can reflect the development, progress, and level of research in this field. This study systematically reviewed the literature published up to 10 years ago on SOC. The number of papers published between 2014 and 2023 has shown a significant increase all over the world. This surge in research output suggests that, in the context of global warming, the study of SOC has garnered increasing attention, reflecting a rapid and robust development in this field. As presented in Figure 1, 3909 studies related to SOC have been published during the past decade. The annual number of publications in this field fluctuates around 300 over the past ten years. Despite minor declines in 2015 and 2019, there has been an overall upward trajectory. The year 2023 has witnessed a significant growth, reaching up 630 articles, accounting for 16.1% of total publications.

3.2. Analysis of Countries, Institutions, and Authors

Crafting a collaboration network can provide deep insights into the interrelationships among researchers, countries, or research institutions within a specific field. In a collaboration network, each node represents an institution, with its size scaled to the number of publications. The purple outer ring signifies the intermediary centrality, where its thickness is indicative of the level of activity and engagement. Lines between nodes indicate collaborative relationships, with thicker lines denoting stronger partnerships. The color and thickness of the rings around each node signify the timing and quantity of publications, respectively. This visual map succinctly captures the essence of scientific collaboration and its temporal progression.
Utilizing CiteSpace software, we performed a comprehensive analysis to identify the key countries, institutions, and authors shaping the landscape of SOC research. After importing the foundational data into CiteSpace and setting a one-year interval for the time span, a national collaboration map was produced with “country” designated as the node type, as shown in Figure 2. The data in Figure 2 demonstrate robust clustering, with a network modularity (Q = 0.5828) above 0.3 and a high network homogeneity (S = 0.8017) over 0.5, indicating the credibility of the clustering result. It is observed that a total of 126 countries have published articles on SOC (N = 126) (Figure 2).
The top 10 countries by publication volume are listed in Table 1, providing a clear overview of the leading contributors in this field. Table 1 illustrates that China leads with a significant number of publications on SOC, totaling 1671 articles, holding 42.7% of the total publications during the past decade. This underscores China’s considerable interest in this subject. The United States follows with 699 publications, while no other country has exceeded 300 articles. Although China has the largest number of publications in this field, its intermediary centrality is much lower, while France and the USA exhibit a very high centrality up to 0.3 and 0.21, respectively, implying that these countries have a significant international influence in this field.
Additionally, China, India, and Brazil are the only developing countries among the top 10 countries with higher publications and centrality, while the rest are all developed countries. The developed countries have more advanced techniques and more research funds to support their research. This might be the reason why developed countries are more advanced in research on SOC.
The top 10 institutions with a high number of publications on SOC during the past decade are ranked in Table 2. It is noticeable that four of the top five institutions with the highest number of publications all come from China. The institution with the most publications is the Chinese Academy of Sciences (644 publications), followed by the University of Chinese Academy of Sciences (249 publications), Ministry of Agriculture and Rural Affairs (162 publications), Northwest A&F University—China (154 publications), Indian Council of Agricultural Research (112 publications).
Centrality is a crucial measure of the closeness of cooperation among institutions, reflecting both the intensity of collaboration and the institution’s influence on others. As demonstrated by the data in Table 2, the Chinese Academy of Sciences stands out with a notably high centrality, signifying its dynamic engagement in collaborative efforts and its substantial contributions to the field of SOC research. The University of Chinese Academy of Sciences follows with 249 publications, marking its notable contribution. Interestingly, Northwest A&F University—China, despite ranking fourth in publication counts, shows a zero intermediary centrality, suggesting that it focuses primarily on independent research, rather than engaging in collaborative efforts. This observation underscores the diversity in research strategies within the academic community studying SOC.
Table 3 highlights the top ten institutions by centrality, with the Consultative Group for International Agricultural Research, Beijing Normal University, and Cornell University leading in intermediary centrality. This suggests a pattern of regular and intimate collaboration with various institutions. However, the top three of the top five institutions with the highest centrality all have a publication number less than 50, with the highest being only 42 articles. (Table 3). This indicates that these institutions should strengthen their collaboration in this community and create an academic atmosphere for interdisciplinary research, which might be a better option for encouraging sustainable development in this field. In contrast, some other institutions, while prolific in their publication output, exhibit a lower degree of centrality in the academic network. The emphasis on inter-institutional communication is crucial for fostering a more interconnected and dynamic research environment. It is suggested that institutions should strengthen their connections and enhance academic exchanges. Otherwise, there is a risk of creating academic barriers between them, which could hinder the free flow of knowledge and collaboration in the scientific community.
The publication counts are indicative of the authors’ significant contributions to the field. The top 10 authors are listed in Table 4. During the past decade, Kuzyakov Yakov stands out with the most publications, followed by Lal Rattan with 16, and Kögel-Knabner Ingrid with 15. The rest of the authors have fewer than 15 publications. Kuzyakov Yakov from the University of Göttingen, Germany, published 27 articles on SOC research. The purpose of these studies mainly focuses on soil carbon turnover and stabilization, microbial ecology, and carbon–nitrogen cycles, as well as long-term field experiments, significantly impacting soil science and global carbon cycle research [57,58,59]. Dr Kuzyakov put forward that C sequestrated in soil derives from microbial necromass and stresses that viruses are decisive for microbial life and functions in soil, thus impacting the stabilization of SOC [60].

3.3. Analysis of Cooperation Networks

Cooperation networks between countries, institutions and authors were analyzed to reveal the global research network in this field. Figure 2 illustrates that China leads in research output on this theme, with the USA, Australia, France, and Canada trailing closely behind. Additionally, the figure highlights the robust collaborative ties that span these nations. For example, China, the USA, India, Pakistan, and France have carried out key cooperations in this field, indicating that developed and developing countries are engaging in scientific research cooperation to address global climate change issues. Among them, China has been at the forefront of international engagement, conducting the most extensive exchanges with its global counterparts. The institutional collaboration map is shown in Figure 3. It is observed that the Chinese Academy of Sciences has the largest node with the most frequent appearances, signifying its substantial presence.
Figure 4 delineates the distribution of author collaboration. Over the past decade, a cumulative total of 509 authors have contributed articles to the WOSCC. Among the authors who published most studies on SOC from 2014 to 2023, the figure also reveals a low network density, specifically 0.004, which suggests a relatively sparse web of connections among researchers. However, where connections are denser, they form small network communities. The more interconnected a community is, the more frequent the communication and collaboration among its members. The graph indicates that such small groups are relatively few in number, suggesting a broad distribution of researchers, with less interconnectedness among teams and a prevalence of individual research efforts. Statistically, among the 509 authors, only one has an intermediary centrality of 0.04, and 19 have an intermediary centrality of 0.01, with the remaining 489 authors scoring zero (Figure 4). This further highlights the lack of close collaboration among authors in this field.

3.4. Co-Citation Analysis of Hot Journals, References, and Authors

When two or more authors, documents, or journals are cited in a third publication at the same time, a co-citation relationship exists among them [55]. In CiteSpace, this analysis is visually represented by nodes, where their size indicates the citation count, and line color denotes the year of the first co-citation. Journal co-citation analysis is instrumental in identifying core journals within a specific field, examining the academic foundations and their evolution over time. The data in Figure 5 exhibit the top 10 most-cited journals, with Soil Biology and Biochemistry topping the list at 3062 citations, Geoderma close behind at 3052, Soil Science Society of America Journal at 2688, Global Change Biology at 2340, and Plant and Soil at 2248. These are the pivotal journals frequently cited by the majority of articles in this domain, underscoring their substantial academic impact.
Interestingly, Acta Oecologica, while cited only 31 times, exhibits the highest intermediary centrality, 0.04, according to Table 5. This indicates a close-knit relationship with other journals, highlighting its significant role in the academic network, despite its lower citation frequency. Thus, both citation frequency and centrality are important to estimate a journal’s academic significance.
Literature co-citation analysis serves as a powerful tool to identify the core influential articles, knowledge structure, and main research areas within a field. Table 6 lists the top 10 most-cited authors in this field from 2014 to 2023. Among them, Lal Rattan (1224), Six Johan (903), Vance Eric D. (508), Lehmann Johannes (469), and Schmid Michael W. I. (459) were the five authors with the highest citation rates in the literature (Table 6), making them the most active researchers in this field. Although Lal Rattan from The Ohio State University, USA, published 16 articles, he is the most co-cited author, with 1224 citations in this field during the past decade. The articles published by Dr Lal have deepened our understanding of soil carbon reservoirs and provided a scientific basis for optimizing soil management to enhance its function as a carbon sink in combating climate change [61,62,63].
From the co-citation analysis, this study also summarized the top 10 most-cited publications in this field (Table 7). The study “Total carbon and nitrogen in the soils of the world” published in European Journal of Soil Science in 2014 was the most cited during the past decade (136 citations) [3], followed by Wiesmeier’s article “Soil organic carbon storage as a key function of soils—A review of drivers and indicators at various scales” in the journal Geoderma in 2019 (134 citations) [5]. Then, “Conceptualizing soil organic matter into particulate and mineral-associated forms to address global change in the 21st century” published in the journal Global Change Biology in 2020 was cited by 126 studies [9]. These references are landmark articles in the field of SOC.

3.5. Keyword Co-Occurrence Network Analysis

The co-occurrence of keywords represents two or more terms appearing together in a single document. The distribution of key research topics can be visually tracked through the co-occurrence of keywords in the literature. This method provides a straightforward way to identify research themes, track hot topics, predict future trends, and gain insights that can inform both research endeavors and decision-making.
By leveraging CiteSpace software, this study has generated a knowledge map that visualizes the most frequently occurring keywords from the corpus of collected literature, as depicted in Figure 6. Each node in the map represents a keyword, with their size proportional to the frequency of occurrence. The higher the frequency is, the more indicative they are of the research hotspots and academic frontiers in the field. The color of the rings around the nodes signifies the years in which the keywords co-occur, while the thickness of the lines indicates the collaborative relationships between keywords. There are a total of 209 nodes (N = 209), and the top 10 most frequent keywords are listed in Table 8. From both Figure 6 and Table 8, we can see that “soil organic carbon” is the most frequently occurring keyword, indicating its widespread attention in the field. Those following are “matter”, “nitrogen”, “sequestration”, “organic carbon”, “dynamics”, “organic matter”, “management”, and “microbial biomass carbon”. This ranking indicates that the research emphasis during the past decade has been heavily focused on the transformation and sequestration of SOC, as well as the application of microbial management strategies in soil.
Emergent terms, which see a sudden increase in usage, are pivotal in reflecting a keyword’s significance in research. Their swift rise can either signal the emergence of a new research frontier or indicate a concept that is swiftly being abandoned. A keyword emergence map helps researchers swiftly pinpoint terms that are under intense scrutiny at a given time, track their popularity, and thus navigate the research landscape effectively. This tool is crucial for identifying trends and hot topics in the field. This study examines the emergence of keywords in this field. By generating a keyword co-occurrence map and adjusting the burst values in the Control Panel, then refreshing and selecting to display 22 burst keywords, the distribution of emergent keywords was mapped in Figure 7. As shown in Figure 7, the term “fluxes” stands out, with the highest burst strength of 7.16, underscoring its considerable prominence and status as a pivotal research focus over the past decade. Its early emergence also suggests that “fluxes” has been a subject of interest in recent years. In 2015, “black carbon” emerged as a hotspot, with the second-highest burst strength, marking a pivotal shift in this field. In terms of duration, “carbon dioxide”, “CO2 efflux”, “vegetation restoration”, and “plant inputs” exhibit the longest spans, indicating their sustained relevance as research hotspots in the field. The most recent burst keywords are “organic manure”, “soil nutrients”, and “winter wheat”, suggesting that current research interests and trends are converging on these specific areas, highlighting their significance in the field.

3.6. Timeline View of Keywords

The time-zone map of keywords reflects the trends of studies on SOC from 2014 to 2023. The data presented in Figure 8 show the initial year and the frequency of the keywords. Larger font sizes for keywords in the map correspond to higher frequencies, signifying greater attention and focus within the field. As indicated in Figure 8, studies on SOC in the past decades mainly focus on carbon sequestration, microbial biomass, and conservation tillage.

4. Discussion

Bibliometric analysis plays a key role in understanding the research dynamics and trends of research fields, which will be helpful for revealing hot topics, research directions, knowledge gaps, and providing guidance for further investigation [71]. Compared with a bibliometric analysis in this field, this study has provided the latest information and updated hotspots and trends in soil carbon. Liu et al. [72] conducted a bibliometric analysis of soil carbon sequestration from 1999 to 2018. In terms of publications, according to Liu et al. [72], the USA has published the most research articles in this field, followed by China and Australia during the three-decade period. However, the observations of Li et al. [73] and Guo et al. [74] both showed that China leads in the research of SOC for a large number of publications, with their search spanning 2012–2022 and 1934–2022, respectively. These results are consistent with our study that China has led in this field from 2014 to 2023. This phenomenon might be closely related with the “Dual Carbon” policy implemented by China. To actively address the global climate change challenge and embody the commitment of a leading nation, China set forth “Peak Carbon Emissions and Carbon Neutrality” (known as “Dual Carbon”) strategic goals in 2020, showcasing its proactive stance in environmental leadership. This policy has encouraged multiple researchers in China to engage in carbon-related research, with the study of SOC being a notable area of focus. Despite having first place in the number of articles, the results in this study show that China is rated with a lower centrality. This indicates that the quality and influence of these publications in China needs to be further improved.
The findings in this study are also in consensus with Li et al. [73] in terms of institutions, who reported that the organization with most publications during the last decade is the Chinese Academy of Sciences, while University of Chinese Academy of Sciences ranks in the second place. It can be seen that these institutions have built close collaborations and significant influences globally. These groups reflect a new characteristic of current institutional collaboration, which is that geographic location has not been a limiting factor in inter-institutional collaboration.
The process of soil carbon sequestration is complex, and the mechanism of SOC transformation and stabilization has been a hotspot in this field. Our findings indicate that the main concerns during the past decade include conservation tillage, carbon sequestration, microbial biomass, and soil aggregates. As reported by Zhang et al. [75], keywords, including carbon sequestration, soil microbial biomass, and nitrogen, have reached a higher research interest, which is in agreement with our findings. In comparison with a similar bibliometric analysis on the topic of soil carbon, the results of this study did not lay emphasis on soil nitrogen, which has been identified as a hot concern in other studies [72]. The effect of soil carbon sequestration is closely related to nitrogen. It is worth exploring in what kind of state the quantity and structure of soil carbon and nitrogen need to be and how much load-bearing capacity soil carbon has for nitrogen. It is suggested that research on SOC should not be limited to soil carbon alone and should pay more attention to the balance between soil carbon and nitrogen.
To be detailed, this study has specified significant patterns in research interest and trends through keyword analysis (Figure 9). The term “conversation tillage” was identified as the most central keyword, indicating its extensive attention within the academic community. Many studies have indicated that conservation tillage practices such as no-tillage or a combination of crop rotation and cover crops facilitate the sequestration of SOC [76,77,78,79,80]. For example, Moussa-Machraoui et al. [79], based on long-term field experiments, found that SOC content increased from 10.0% to 22.2% under no-tillage conditions compared to plowing. Iheshiulo et al. [80] revealed that rotations combined with conservation tillage performed better in enhancing soil aggregation compared to using conventional tillage. However, there is no consensus on conservation tillage. Some researchers have reported that no-tillage practices can lead to reduced crop yields, especially in eco-fragile regions [81,82]. The long-term implementation of no-tillage is not conducive to deep root cultivation, which will make the cultivated layer of farmland shallower and increase soil compaction [83]. Therefore, it is essential to explore how to combine and optimize various conversation management practices to achieve optimal grain yield and carbon sequestration.
Current research on SOC has shifted from macroscopic trends to explanations based on micro-level biological dynamics [75,84]. In this study, frequently occurring and highly central keywords also include “carbon sequestration”, “microbial biomass”, “soil respiration”, and “aggregate stability”, which suggests that the research focus has revolved around carbon sequestration during the past decade, but researchers need to start paying more attention to its mechanisms, especially microorganism participation [85,86,87,88,89]. Numerous studies have highlighted an extremely significant correlation between the content of microbial biomass carbon and the SOC mineralization [90]. Microbial biomass carbon is the most reactive and labile component within soil organic matter, playing a pivotal role despite its relatively small proportion in the soil carbon reservoir [33]. The process of SOC mineralization is accompanied by soil respiration, a vital metabolic activity where microorganisms break down carbon in organic matter. In aerobic conditions, these microorganisms engage in respiration that results in the emission of CO2. Conversely, under anaerobic conditions, they produce methane (CH4) and other greenhouse gases, thereby facilitating the process of carbon decomposition [91]. According to Zhou et al. [92], microorganisms play an important role in regulating SOC dynamics, and thus it is essential to elucidate micro-mediated feedbacks for understanding ecosystem responses to global climate change. Despite these focused studies, the specific roles of microorganisms and the effects in SOC mineralization processes are still not fully understood. Future research should concentrate on elucidating the intrinsic mechanisms of SOC dynamics from the micro-level perspectives. This is crucial for the development of more accurate models for carbon cycling in soils and for devising effective strategies to enhance soil carbon sequestration and combat climate change.

5. Conclusions and Challenges

This study summarized recent development in the field of SOC during the past decade. The study of this subject has been growing fast between 2014 and 2023. The number of publications has experienced a rapid growth, which indicates that research on SOC has gradually attracted the attention of researchers. China leads with the highest number of publications but has a low centrality, implying that the quality and influence of these publications in China need to be further improved. France and the USA have a considerable international influence in this field, with a centrality much higher than other countries. Yakov Kuzyakov from Germany contributed the most articles, with 27 articles published in this field. Rattan Lal is the most co-cited author, with 1224 citations during the past decade. Soil Biology and Biochemistry, Geoderma, Soil Science Society of America Journal, Global Change Biology and Plant and Soil ranked as the most influential journals. Conservation tillage, carbon sequestration, microbial biomass and soil aggregate have all arisen and gradually become hotspots in the last ten years. The mechanism of SOC dynamics under different conditions will be of continuous concern due to increasing global warming.
Through CiteSpace bibliometric analysis, this study provides valuable insights into the research dynamics and future trends in the field of SOC. However, there are limitations. Firstly, this study was confined to the WOSCC database. Although this database encompasses the majority of high-quality research papers, the results may omit related research in other databases such as Scopus and CNKI, and could lead to potential bias and fragmentation. Secondly, despite the publications concentrated on original research articles and review articles, the total number of publications is still relatively high. More stringent principles should be set to pick out more focused publications. Finally, since this study set the article type as research and review articles, other formats like chapters, letters, and conference publications were excluded, which may have led to bias. Despite these potential limitations, this study benefits from the reputable WOSCC database and the extensive analysis of publications, enabling it to effectively illustrate the evolution and trends of SOC research. Future research within similar topics should address these limitations to provide a more precise and comprehensive analysis. This study provides insights into the current status and trends of SOC research, helping scholars with a better understanding of the rapidly advancing subject.

Author Contributions

Conceptualization, M.F. and J.W.; methodology, W.Y. and M.S.; software, W.Y.; writing—original draft preparation, W.Y. and M.F.; writing—review and editing, J.W., H.Z. and Z.Y.; supervision, J.W.; project administration, J.W.; funding acquisition, M.F., J.W. and Z.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (Grant No: 42101062), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No: 22KJB170008) and the Humanity and Social Science Foundation of Ministry of Education of China (Grant No: 22YJAZH135).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Fornara, D.A.; Steinbeiss, S.; McNamara, N.P.; Gleixner, G.; Oakley, S.; Poulton, P.R.; Macdonald, A.J.; Bardgett, R.D. Increases in soil organic carbon sequestration can reduce the global warming potential of long-term liming to permanent grassland. Glob. Change Biol. 2011, 17, 1925–1934. [Google Scholar] [CrossRef]
  2. Tifafi, M.; Guenet, B.; Hatté, C. Large differences in global and regional total soil carbon stock estimates based on soil grids, HWSD, and NCSCD: Intercomparison and evaluation based on field data from USA, England, Wales, and France. Glob. Biogeochem. Cycles 2018, 32, 42–56. [Google Scholar] [CrossRef]
  3. Batjes, N.H. Total carbon and nitrogen in the soils of the world. Eur. J. Soil Sci. 1996, 47, 151–163. [Google Scholar] [CrossRef]
  4. Lal, R. Soil carbon sequestration impacts on global climate change and food security. Science 2004, 304, 1623–1627. [Google Scholar] [CrossRef] [PubMed]
  5. Wiesmeier, M.; Urbanski, L.; Hobley, E.; Lang, B.; von Lützow, M.; Marin-Spiotta, E.; van Wesemael, B.; Rabot, E.; Ließ, M.; Garcia-Franco, N.; et al. Soil organic carbon storage as a key function of soils—A review of drivers and indicators at various scales. Geoderma 2019, 333, 149–162. [Google Scholar] [CrossRef]
  6. Zhang, H.; Wu, P.; Fan, M.; Zheng, S.; Wu, J.; Yang, X.; Zhang, M.; Yin, A.; Gao, C. Dynamics and driving factors of the organic carbon fractions in agricultural land reclaimed from coastal wetlands in eastern China. Ecol. Indic. 2018, 89, 639–647. [Google Scholar] [CrossRef]
  7. Hungate, B.A.; Van Groenigen, K.J.; Six, J.; Jastrow, J.D.; Luo, Y.; De GRAAFF, M.A.; van Kessel, C.; Osenberg, C.W. Assessing the effect of elevated carbon dioxide on soil carbon: A comparison of four meta-analyses. Glob. Change Biol. 2009, 15, 2020–2034. [Google Scholar] [CrossRef]
  8. Nerger, R.; Klüver, K.; Cordsen, E.; Fohrer, N. Intensive long-term monitoring of soil organic carbon and nutrients in Northern Germany. Nutr. Cycl. Agroecosyst. 2020, 116, 57–69. [Google Scholar] [CrossRef]
  9. Lavallee, J.M.; Soong, J.L.; Cotrufo, M.F. Conceptualizing soil organic matter into particulate and mineral-associated forms to address global change in the 21st century. Glob. Change Biol. 2020, 26, 261–273. [Google Scholar] [CrossRef]
  10. Zhou, Y.; Hartemink, A.E.; Shi, Z.; Liang, Z.; Lu, Y. Land use and climate change effects on soil organic carbon in North and Northeast China. Sci. Total Environ. 2019, 647, 1230–1238. [Google Scholar] [CrossRef]
  11. Stockmann, U.; Adams, M.A.; Crawford, J.W.; Field, D.J.; Henakaarchchi, N.; Jenkins, M.; Minasny, B.; McBratney, A.B.; De Courcelles, V.D.R.; Singh, K.; et al. The knowns, known unknowns and unknowns of sequestration of soil organic carbon. Agric. Ecosyst. Environ. 2013, 164, 80–99. [Google Scholar] [CrossRef]
  12. Tao, F.; Palosuo, T.; Valkama, E.; Mäkipää, R. Cropland soils in China have a large potential for carbon sequestration based on literature survey. Soil Tillage Res. 2019, 186, 70–78. [Google Scholar] [CrossRef]
  13. Fan, M.; Lal, R.; Zhang, H.; Margenot, A.J.; Wu, J.; Wu, P.; Zhang, L.; Yao, J.; Chen, F.; Gao, C. Variability and determinants of soil organic matter under different land uses and soil types in eastern China. Soil Tillage Res. 2020, 198, 104544. [Google Scholar] [CrossRef]
  14. Raza, S.; Irshad, A.; Margenot, A.; Zamanian, K.; Li, N.; Ullah, S.; Mehmood, K.; Khan, M.A.; Siddique, N.; Zhou, J.; et al. Inorganic carbon is overlooked in global soil carbon research: A bibliometric analysis. Geoderma 2024, 443, 116831. [Google Scholar] [CrossRef] [PubMed]
  15. Lozano-García, B.; Muñoz-Rojas, M.; Parras-Alcántara, L. Climate and land use changes effects on soil organic carbon stocks in a Mediterranean semi-natural area. Sci. Total Environ. 2017, 579, 1249–1259. [Google Scholar] [CrossRef]
  16. Ferdush, J.; Paul, V. A review on the possible factors influencing soil inorganic carbon under elevated CO2. Catena 2021, 204, 105434. [Google Scholar] [CrossRef]
  17. Ferreira, A.C.C.; Leite, L.F.C.; de Araújo, A.S.F.; Eisenhauer, N. Land-use type effects on soil organic carbon and microbial properties in a semi-arid region of northeast Brazil. Land Degrad. Dev. 2016, 27, 171–178. [Google Scholar] [CrossRef]
  18. Kögel-Knabner, I. The macromolecular organic composition of plant and microbial residues as inputs to soil organic matter: Fourteen years on. Soil Biol. Biochem. 2017, 105, A3–A8. [Google Scholar] [CrossRef]
  19. Six, J.; Paustian, K. Aggregate-associated soil organic matter as an ecosystem property and a measurement tool. Soil Biol. Biochem. 2014, 68, A4–A9. [Google Scholar] [CrossRef]
  20. Yan, Z.; Zhou, J.; Liu, C.; Jia, R.; Mganga, K.Z.; Yang, L.; Yang, Y.; Peixoto, L.; Zang, H.; Zeng, Z. Legume-based crop diversification reinforces soil health and carbon storage driven by microbial biomass and aggregates. Soil Tillage Res. 2023, 234, 105848. [Google Scholar] [CrossRef]
  21. Jastrow, J.D. Soil aggregate formation and the accrual of particulate and mineral-associated organic matter. Soil Biol. Biochem. 1996, 28, 665–676. [Google Scholar] [CrossRef]
  22. Abiven, S.; Menasseri, S.; Chenu, C. The effects of organic inputs over time on soil aggregate stability—A literature analysis. Soil Biol. Biochem. 2009, 41, 1–12. [Google Scholar] [CrossRef]
  23. Zhang, Q.; Liu, H.; Liang, Y.; Liang, Y.; Zhao, Y.; Wang, Z.; Li, Y.; Liu, W.; Wang, X.; Yang, G.; et al. The multifunctionality of soil aggregates is related to the complexity of aggregate microbial community during afforestation. Catena 2024, 236, 107737. [Google Scholar] [CrossRef]
  24. Zhang, W.; Munkholm, L.J.; Liu, X.; An, T.; Xu, Y.; Ge, Z.; Xie, N.; Li, A.; Dong, Y.; Peng, C.; et al. Soil aggregate microstructure and microbial community structure mediate soil organic carbon accumulation: Evidence from one-year field experiment. Geoderma 2023, 430, 116324. [Google Scholar] [CrossRef]
  25. Liu, S.; Zhang, Y.; Zong, Y. Response of soil carbon dioxide fluxes, soil organic carbon and microbial biomass carbon to biochar amendment: A meta-analysis. Glob. Change Biol. Bioenergy 2016, 8, 392–406. [Google Scholar] [CrossRef]
  26. Barreto, R.C.; Madari, B.E.; Maddock, J.E.; Machado, P.L.; Torres, E.; Franchini, J.; Costa, A.R. The impact of soil management on aggregation, carbon stabilization and carbon loss as CO2 in the surface layer of a Rhodic Ferralsol in Southern Brazil. Agric. Ecosyst. Environ. 2009, 132, 243–251. [Google Scholar] [CrossRef]
  27. Xia, L.; Lam, S.K.; Yan, X.; Chen, D. How does recycling of livestock manure in agroecosystems affect crop productivity, reactive nitrogen losses, and soil carbon balance? Environ. Sci. Technol. 2017, 51, 7450–7457. [Google Scholar] [CrossRef]
  28. Zhu, E.; Deng, J.; Zhou, M.; Gan, M.; Jiang, R.; Wang, K.; Shahtahmassebi, A. Carbon emissions induced by land-use and land-cover change from 1970 to 2010 in Zhejiang, China. Sci. Total Environ. 2019, 646, 930–939. [Google Scholar] [CrossRef]
  29. Liu, C.; Lu, M.; Cui, J.; Li, B.; Fang, C. Effects of straw carbon input on carbon dynamics in agricultural soils: A meta-analysis. Global Change Biol. 2014, 20, 1366–1381. [Google Scholar] [CrossRef]
  30. Whitehead, D.; Schipper, L.A.; Pronger, J.; Moinet, G.Y.; Mudge, P.L.; Pereira, R.C.; Kirschbaum, M.U.; McNally, S.R.; Beare, M.H.; Camps-Arbestain, M. Management practices to reduce losses or increase soil carbon stocks in temperate grazed grasslands: New Zealand as a case study. Agric. Ecosyst. Environ. 2018, 265, 432–443. [Google Scholar] [CrossRef]
  31. Zhao, Y.; Wang, M.; Hu, S.; Zhang, X.; Ouyang, Z.; Zhang, G.; Huang, B.; Zhao, S.; Wu, J.; Xie, D.; et al. Economics-and policy-driven organic carbon input enhancement dominates soil organic carbon accumulation in Chinese croplands. Proc. Natl. Acad. Sci. USA 2018, 115, 4045–4050. [Google Scholar] [CrossRef] [PubMed]
  32. Lugato, E.; Paustian, K.; Panagos, P.; Jones, A.; Borrelli, P. Quantifying the erosion effect on current carbon budget of European agricultural soils at high spatial resolution. Glob. Change Biol. 2016, 22, 1976–1984. [Google Scholar] [CrossRef] [PubMed]
  33. Schnecker, J.; Baldaszti, L.; Gündler, P.; Pleitner, M.; Sandén, T.; Simon, E.; Spiegel, F.; Spiegel, H.; Malo, C.U.; Zechmeister-Boltenstern, S.; et al. Seasonal dynamics of soil microbial growth, respiration, biomass, and carbon use efficiency in temperate soils. Geoderma 2023, 440, 116693. [Google Scholar] [CrossRef]
  34. Phillips, C.L.; Bond-Lamberty, B.; Desai, A.R.; Lavoie, M.; Risk, D.; Tang, J.; Todd-Brown, K.; Vargas, R. The value of soil respiration measurements for interpreting and modeling terrestrial carbon cycling. Plant Soil. 2017, 413, 1–25. [Google Scholar] [CrossRef]
  35. Hu, J.; Guan, X.; Liang, X.; Wang, B.; Chen, X.; He, X.; Xie, J.; Deng, G.; Chen, J.; Li, X.; et al. Optimizing the Nitrogen Fertilizer Management to Maximize the Benefit of Straw Returning on Early Rice Yield by Modulating Soil N Availability. Agriculture 2024, 14, 1168. [Google Scholar] [CrossRef]
  36. Wang, X.; Li, Y.; Gong, X.; Niu, Y.; Chen, Y.; Shi, X.; Li, W. Storage, pattern and driving factors of soil organic carbon in an ecologically fragile zone of northern China. Geoderma 2019, 343, 155–165. [Google Scholar] [CrossRef]
  37. Gonçalves, D.R.P.; de Moraes Sá, J.C.; Mishra, U.; Cerri, C.E.P.; Ferreira, L.A.; Furlan, F.J.F. Soil type and texture impacts on soil organic carbon storage in a sub-tropical agro-ecosystem. Geoderma 2017, 286, 88–97. [Google Scholar] [CrossRef]
  38. Hassan, W.; Bano, R.; Khatak, B.U.; Hussain, I.; Yousaf, M.; David, J. Temperature sensitivity and soil organic carbon pools decomposition under different moisture regimes: Effect on total microbial and enzymatic activity. Clean Soil Air Water. 2015, 43, 391–398. [Google Scholar] [CrossRef]
  39. Chi, Y.; Shi, H.; Zheng, W.; Sun, J. Simulating spatial distribution of coastal soil carbon content using a comprehensive land surface factor system based on remote sensing. Sci. Total Environ. 2018, 628–629, 384–399. [Google Scholar] [CrossRef]
  40. Le Noë, J.; Billen, G.; Garnier, J. Carbon dioxide emission and soil sequestration for the French agro-food system: Present and prospective scenarios. Front. Sustain. Food Syst. 2019, 3, 19. [Google Scholar] [CrossRef]
  41. Vitharana, U.W.A.; Mishra, U.; Mapa, R.B. National soil organic carbon estimates can improve global estimates. Geoderma 2019, 337, 55–64. [Google Scholar] [CrossRef]
  42. Zhang, L.; Zheng, Q.; Liu, Y.; Liu, S.; Yu, D.; Shi, X.; Xing, S.; Chen, H.; Fan, X. Combined effects of temperature and precipitation on soil organic carbon changes in the uplands of eastern China. Geoderma 2019, 337, 1105–1115. [Google Scholar] [CrossRef]
  43. Martín, J.A.R.; Álvaro-Fuentes, J.; Gabriel, J.L.; Gutiérrez, C.; Nanos, N.; Escuer, M.; Ramos-Miras, J.J.; Gil, C.; Martín-Lammerding, D.; Boluda, R. Soil organic carbon stock on the Majorca Island: Temporal change in agricultural soil over the last 10 years. Catena 2019, 181, 104087. [Google Scholar] [CrossRef]
  44. Wei, X.; Shao, M.; Gale, W.; Li, L. Global pattern of soil carbon losses due to the conversion of forests to agricultural land. Sci. Rep. 2014, 4, 4062. [Google Scholar] [CrossRef]
  45. Ashworth, A.J.; Allen, F.L.; Wight, J.P.; Saxton, A.M.; Tyler, D.D.; Sams, C.E. Soil organic carbon sequestration rates under crop sequence diversity, bio-covers, and no-tillage. Soil Sci. Soc. Am. J. 2014, 78, 1726–1733. [Google Scholar] [CrossRef]
  46. Nicoloso, R.S.; Rice, C.W.; Amado, T.J.C.; Costa, C.N.; Akley, E.K. Carbon saturation and translocation in a no-till soil under organic amendments. Agric. Ecosyst. Environ. 2018, 264, 73–84. [Google Scholar] [CrossRef]
  47. Pareja-Sánchez, E.; Plaza-Bonilla, D.; Ramos, M.C.; Lampurlanés, J.; Álvaro-Fuentes, J.; Cantero-Martínez, C. Long-term no-till as a means to maintain soil surface structure in an agroecosystem transformed into irrigation. Soil Tillage Res. 2017, 174, 221–230. [Google Scholar] [CrossRef]
  48. Margenot, A.J.; Pulleman, M.M.; Sommer, R.; Paul, B.K.; Parikh, S.J.; Jackson, L.E.; Fonte, S.J. Biochemical proxies indicate differences in soil C cycling induced by long-term tillage and residue management in a tropical agroecosystem. Plant Soil. 2017, 420, 315–329. [Google Scholar] [CrossRef]
  49. Tian, D.; Xiang, Y.; Seabloom, E.; Wang, J.; Jia, X.; Li, T.; Li, Z.; Yang, J.; Guo, H.; Niu, S. Soil carbon sequestration benefits of active versus natural restoration vary with initial carbon content and soil layer. Commun. Earth Environ. 2023, 4, 83. [Google Scholar] [CrossRef]
  50. He, W.; Yang, J.Y.; Drury, C.F.; Smith, W.N.; Grant, B.B.; He, P.; Qian, B.; Zhou, W.; Hoogenboom, G. Estimating the impacts of climate change on crop yields and N2O emissions for conventional and no-tillage in Southwestern Ontario, Canada. Agric. Syst. 2018, 159, 187–198. [Google Scholar] [CrossRef]
  51. Chen, C. CiteSpace II: Detecting and visualizing emerging trends and transient patterns in scientific literature. J. Am. Soc. Inf. Sci. Technol. 2006, 57, 359–377. [Google Scholar] [CrossRef]
  52. Hu, Y.; Yang, S.; Qian, X.; Li, Z.; Fan, Y.; Manevski, K.; Chen, Y.; Gao, W. Bibliometric network analysis of crop yield gap research over the past three decades. Agriculture 2023, 13, 2105. [Google Scholar] [CrossRef]
  53. Zhang, F.; Liu, Y.; Zhang, Y. Bibliometric analysis of research trends in agricultural soil organic carbon mineralization from 2000 to 2022. Agriculture 2023, 13, 1248. [Google Scholar] [CrossRef]
  54. Wang, C.; Deng, L.; Zhang, Y.; Zhao, M.; Liang, M.; Lee, L.C.; Cristhian, C.O.; Yang, L.; He, T. Farmland phytoremediation in bibliometric analysis. J. Environ. Manag. 2024, 351, 119971. [Google Scholar] [CrossRef] [PubMed]
  55. Zhang, K.; Liu, F.; Zhang, H.; Duan, Y.; Luo, J.; Sun, X.; Wang, M.; Ye, D.; Wang, M.; Zhu, Z.; et al. Trends in phytoremediation of heavy metals-contaminated soils: A web of science and CiteSpace bibliometric analysis. Chemosphere 2024, 352, 141293. [Google Scholar] [CrossRef]
  56. Li, Z.; Kong, L.; Hu, L.; <monospace> </monospace>Wei, J.; Zhang, X.; Guo, W.; Shi, W. Greenhouse gas emissions from constructed wetlands: A bibliometric analysis and mini-review. Sci. Total Environ. 2023, 906, 167582. [Google Scholar] [CrossRef]
  57. Kuzyakov, Y.; Blagodatskaya, E. Microbial hotspots and hot moments in soil: Concept & review. Soil Biol. Biochem. 2015, 83, 184–199. [Google Scholar] [CrossRef]
  58. Pausch, J.; Kuzyakov, Y. Carbon input by roots into the soil: Quantification of rhizodeposition from root to ecosystem scale. Glob. Change Biol. 2018, 24, 1–12. [Google Scholar] [CrossRef]
  59. Kuzyakov, Y.; Bogomolova, I.; Glaser, B. Biochar stability in soil: Decomposition during eight years and transformation as assessed by compound-specific 14C analysis. Soil Biol. Biochem. 2014, 70, 229–236. [Google Scholar] [CrossRef]
  60. Kuzyakov, Y.; Mason-Jones, K. Viruses in soil: Nano-scale undead drivers of microbial life, biogeochemical turnover and ecosystem functions. Soil Biol. Biochem. 2018, 127, 305–317. [Google Scholar] [CrossRef]
  61. Lal, R. Carbon farming by recarbonization of agroecosystems. Pedosphere 2023, 33, 676–679. [Google Scholar] [CrossRef]
  62. Lal, R. Fate of Soil Carbon Transported by Erosional Processes. Appl. Sci. 2022, 12, 48. [Google Scholar] [CrossRef]
  63. Lal, R. Food security impacts of the “4 per Thousand” initiative. Geoderma 2020, 374, 114427. [Google Scholar] [CrossRef]
  64. Minasny, B.; Malone, B.P.; McBratney, A.B.; Angers, D.A.; Arrouays, D.; Chambers, A.; Chaplot, V.; Chen, Z.S.; Cheng, K.; Das, B.S.; et al. Soil carbon 4 per mille. Geoderma 2017, 292, 59–86. [Google Scholar] [CrossRef]
  65. Cotrufo, M.F.; Ranalli, M.G.; Haddix, M.L.; Six, J.; Lugato, E. Soil carbon storage informed by particulate and mineral-associated organic matter. Nat. Geosci. 2019, 12, 989–994. [Google Scholar] [CrossRef]
  66. Lehmann, J.; Kleber, M. The contentious nature of soil organic matter. Nature 2015, 528, 60–68. [Google Scholar] [CrossRef]
  67. Liang, C.; Amelung, W.; Lehmann, J.; Kästner, M. Quantitative assessment of microbial necromass contribution to soil organic matter. Glob. Change Biol. 2019, 25, 3578–3590. [Google Scholar] [CrossRef]
  68. Liang, C.; Schimel, J.P.; Jastrow, J.D. The importance of anabolism in microbial control over soil carbon storage. Nat. Microbiol. 2017, 2, 17105. [Google Scholar] [CrossRef]
  69. Schmidt, M.W.; Torn, M.S.; Abiven, S.; Dittmar, T.; Guggenberger, G.; Janssens, I.A.; Kleber, M.; Kögel-Knabner, I.; Lehmann, J.; Manning, D.A.; et al. Persistence of soil organic matter as an ecosystem property. Nature 2011, 478, 49–56. [Google Scholar] [CrossRef]
  70. Rowley, M.C.; Grand, S.; Verrecchia, É.P. Calcium-mediated stabilisation of soil organic carbon. Biogeochemistry 2018, 137, 27–49. [Google Scholar] [CrossRef]
  71. Ye, H.; Du, Y.; Jin, Y.; Liu, F.; He, S.; Guo, Y. Articles on hemorrhagic shock published between 2000 and 2021: A CiteSpace-Based bibliometric analysis. Heliyon 2023, 9, e18840. [Google Scholar] [CrossRef] [PubMed]
  72. Liu, B.; Li, X.; Chen, L.; Pang, D.B.; Zhu, Z.Y.; Liu, L.Z.; Wu, M.Y. Research progress on soil carbon sequestration based on bibliometric analysis. Chin. J. Soil Sci. 2021, 52, 211–220. (In Chinese) [Google Scholar] [CrossRef]
  73. Li, B.; Chen, L.; Pang, D.; Li, X. Research progress of soil organic carbon in recent 11 years based on bibliometric analysis. J. Chin. Agri. Univ. 2024, 29, 138–151. (In Chinese) [Google Scholar] [CrossRef]
  74. Guo, L.; Nkoh, J.; Xu, R.K. A critical review of the interactions of organic carbon components with soil minerals: Insight from bibliometric analysis of the environmental behaviors of heavy metal(loid)s. J. Soil. Sediment. 2023, 23, 2396–2416. [Google Scholar] [CrossRef]
  75. Zhang, T.; Tang, Y.; Li, H.; Hu, W.; Cheng, J.; Lee, X. A bibliometric review of biochar for soil carbon sequestration and mitigation from 2001 to 2020. Ecotox. Environ. Saf. 2023, 264, 115438. [Google Scholar] [CrossRef]
  76. Pareja-Sánchez, E.; Domouso, P.; Gómez-Muñoz, B.; Heras-Linares, M.T.; García-Ruíz, R. Conservation practices boost soil-protected organic carbon stocks in olive orchards. Agriculture 2024, 14, 1354. [Google Scholar] [CrossRef]
  77. Gonçalves, D.R.P.; de Moraes Sá, J.C.; Mishra, U.; Fornari, A.J.; Furlan, F.J.F.; Ferreira, L.A.; Inagaki, T.M.; Romaniw, J.; de Oliveira Ferreira, A.; Briedis, C. Conservation agriculture based on diversified and high-performance production system leads to soil carbon sequestration in subtropical environments. J. Clean. Prod. 2019, 219, 136–147. [Google Scholar] [CrossRef]
  78. Jarecki, M.; Grant, B.; Smith, W.; Deen, B.; Drury, C.; VanderZaag, A.; Qian, B.; Yang, J.; Wagner-Riddle, C. Long-term trends in corn yields and soil carbon under diversified crop rotations. J. Environ. Qual. 2018, 47, 635–643. [Google Scholar] [CrossRef]
  79. Moussa-Machraoui, S.B.; Errouissi, F.; Ben-Hammouda, M.; Nouira, S. Comparative effects of conventional and no-tillage management on some soil properties under Mediterranean semi-arid conditions in northwestern Tunisia. Soil Tillage Res. 2010, 106, 247–253. [Google Scholar] [CrossRef]
  80. Iheshiulo, E.M.-A.; Larney, F.J.; Hernandez-Ramirez, G.; Luce, M.S.; Chau, H.W.; Liu, K. Crop rotations influence soil hydraulic and physical quality under no-till on the Canadian prairies. Agric. Ecosyst. Environ. 2024, 361, 108820. [Google Scholar] [CrossRef]
  81. Pittelow, C.M.; Liang, X.Q.; Linquist, B.A.; Van Groenigen, K.J.; Lee, J.; Lundy, M.E.; Van Gestel, N.; Six, J.; Venterea, R.T.; Van Kessel, C. Productivity limits and potentials of the principles of conservation agriculture. Nature 2015, 517, 365–368. [Google Scholar] [CrossRef] [PubMed]
  82. Sommer, R.; Paul, B.K.; Mukalama, J.; Kihara, J. Reducing losses but failing to sequester carbon in soils—The case of conservation agriculture and integrated soil fertility management in the humid tropical agro-ecosystem of Western Kenya. Agric. Ecosyst. Environ. 2018, 254, 82–91. [Google Scholar] [CrossRef]
  83. Pittelkow, C.M.; Linquist, B.A.; Lundy, M.E.; Liang, X.; Van Groenigen, K.J.; Lee, J.; Van Gestel, N.; Six, J.; Venterea, R.T.; Van Kessel, C. When does no-till yield more? A global meta-analysis. Field Crops Res. 2015, 183, 156–168. [Google Scholar] [CrossRef]
  84. Tian, J.; Dungait, J.A.; Hou, R.; Deng, Y.; Hartley, I.P.; Yang, Y.; Kuzyakov, Y.; Zhang, F.; Cotrufo, M.F.; Zhou, J. Microbially mediated mechanisms underlie soil carbon accrual by conservation agriculture under decade-long warming. Nat. Commun. 2024, 15, 377. [Google Scholar] [CrossRef]
  85. Cao, X.H.; Long, H.Y.; Lei, Q.L.; Jian, L.I.U.; Zhang, J.Z.; Zhang, W.J.; Wu, S.X. Spatio-temporal variations in organic carbon density and carbon sequestration potential in the topsoil of Hebei Province, China. J. Integr. Agric. 2016, 15, 2627–2638. [Google Scholar] [CrossRef]
  86. Chen, S.; Martin, M.P.; Saby, N.P.A.; Walter, C.; Angers, D.A.; Arrouays, D. Fine resolution map of top- and subsoil carbon sequestration potential in France. Sci. Total Environ. 2018, 630, 389–400. [Google Scholar] [CrossRef]
  87. Fang, J.; Yu, G.; Liu, L.; Hu, S.; Chapin III, F.S. Climate change, human impacts, and carbon sequestration in China. Proc. Natl. Acad. Sci. USA 2018, 115, 4015–4020. [Google Scholar] [CrossRef]
  88. Huang, X.; Tang, H.; Kang, W.; Yu, G.; Ran, W.; Hong, J.; Shen, Q. Redox interface-associated organo-mineral interactions: A mechanism for C sequestration under a rice-wheat cropping system. Soil Biol. Biochem. 2018, 120, 12–23. [Google Scholar] [CrossRef]
  89. Mason, A.R.G.; Salomon, M.J.; Lowe, A.J.; Cavagnaro, T.R. Microbial solutions to soil carbon sequestration. J. Clean. Prod. 2023, 417, 137993. [Google Scholar] [CrossRef]
  90. Devêvre, O.C.; Horwáth, W.R. Decomposition of rice straw and microbial carbon use efficiency under different soil temperatures and moistures. Soil Biol. Biochem. 2000, 32, 1773–1785. [Google Scholar] [CrossRef]
  91. Guo, J.; Xiong, W.; Qiu, J.; Wang, G. Linking soil organic carbon mineralization to soil physicochemical properties and bacterial alpha diversity at different depths following land use changes. Ecol. Process. 2023, 12, 39. [Google Scholar] [CrossRef]
  92. Zhou, J.; Xue, K.; Xie, J.; Deng, Y.E.; Wu, L.; Cheng, X.; Fei, S.; Deng, S.; He, Z.; Van Nostrand, J.D.; et al. Microbial mediation of carbon-cycle feedbacks to climate warming. Nat. Clim. Change 2012, 2, 106–110. [Google Scholar] [CrossRef]
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Figure 1. Changes in the annual number and cumulative number of soil organic carbon publications from 2014 to 2023.
Figure 1. Changes in the annual number and cumulative number of soil organic carbon publications from 2014 to 2023.
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Figure 2. Map of countries involved in soil organic carbon research from 2014 to 2023.
Figure 2. Map of countries involved in soil organic carbon research from 2014 to 2023.
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Figure 3. Collaborative network of institutions researching soil organic carbon from 2014 to 2023.
Figure 3. Collaborative network of institutions researching soil organic carbon from 2014 to 2023.
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Figure 4. Collaborative network of authors researching soil organic carbon from 2014 to 2023.
Figure 4. Collaborative network of authors researching soil organic carbon from 2014 to 2023.
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Figure 5. Top 10 journals in terms of publication citations on soil organic carbon research from 2014 to 2023.
Figure 5. Top 10 journals in terms of publication citations on soil organic carbon research from 2014 to 2023.
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Figure 6. Mapping of keyword co-occurrence on soil organic carbon from 2014 to 2023.
Figure 6. Mapping of keyword co-occurrence on soil organic carbon from 2014 to 2023.
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Figure 7. Top 22 keywords with the strongest citation bursts on soil organic carbon research from 2014 to 2023.
Figure 7. Top 22 keywords with the strongest citation bursts on soil organic carbon research from 2014 to 2023.
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Figure 8. Time-zone map of keywords on soil organic carbon research from 2014 to 2023.
Figure 8. Time-zone map of keywords on soil organic carbon research from 2014 to 2023.
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Figure 9. Cluster map of keywords for research on soil organic carbon from 2014 to 2023.
Figure 9. Cluster map of keywords for research on soil organic carbon from 2014 to 2023.
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Table 1. Top 10 countries in terms of publications on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the country.
Table 1. Top 10 countries in terms of publications on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the country.
RankCountryPublicationsCentralityYear
1CHINA16710.12014
2USA6990.212014
3GERMANY2900.12014
4INDIA2600.052014
5AUSTRALIA2490.12014
6SPAIN1950.052014
7BRAZIL1750.072014
8FRANCE1690.332014
9CANADA1570.132014
10ENGLAND1380.092014
Table 2. Top 10 institutions in terms of publications on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the organization.
Table 2. Top 10 institutions in terms of publications on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the organization.
RankOrganizationCountryPublicationsCentralityYear
1Chinese Academy of SciencesCHINA6440.092014
2University of Chinese Academy of SciencesCHINA2490.032014
3Ministry of Agriculture and Rural AffairsCHINA1620.022014
4Northwest A&F University—ChinaCHINA15402014
5Indian Council of Agricultural ResearchINDIA1120.092014
6Institut National de Recherche en Agriculture, Alimentation et EnvironnementFRANCE1100.022014
7Chinese Academy of Agricultural SciencesCHINA1040.042014
8Chinese Academy of Sciences and Ministry of Water ResourcesCHINA910.022014
9United States Department of EnergyUSA820.062014
10Centre National de la Recherche ScientifiqueFRANCE810.032014
Table 3. Top 10 institutions in terms of publication centrality on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the organization. “–” means this is an international organization.
Table 3. Top 10 institutions in terms of publication centrality on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the organization. “–” means this is an international organization.
RankOrganizationCountryCentralityPublicationsYear
1Consultative Group for International Agricultural Research–0.11252016
2Beijing Normal UniversityCHINA0.1422014
3Cornell UniversityUSA0.1232014
4Chinese Academy of SciencesCHINA0.096442014
5Indian Council of Agricultural ResearchINDIA0.091122014
6United States Department of AgricultureUSA0.08752014
7Wageningen University & ResearchNETHERLANDS0.08482014
8Commonwealth Scientific and Industrial Research OrganisationAUSTRALIA0.08432014
9Agriculture and Agri-Food CanadaCANADA0.08332014
10University of QueenslandAUSTRALIA0.08212016
Table 4. Top 10 authors in terms of publication number on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term.
Table 4. Top 10 authors in terms of publication number on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term.
RankAuthorCountryAffiliationPublicationsCentralityYear
1Kuzyakov, YakovGERMANYUniversity of Göttingen270.042015
2Lal, RattanUSAThe Ohio State University1602014
3Kögel-knabner, IngridGERMANYTechnische Universität München1502014
4Ge, TidaCHINANingbo University130.012015
5Ding, XiaodongCHINAQingdao Agricultural University1102021
6Zhang, ShirongCHINASichuan Agricultural University1102021
7Pereira, Marcos GervasioBRAZILFederal Rural University of Rio de Janeiro1102017
8Chenu, ClaireFRANCEInstitut National de Recherche en Agriculture, Alimentation et Environnement1002016
9Dymov, AlexeyRUSSIARussian Academy of Sciences1002015
10Li, PengCHINAJiangxi Agricultural University90.012020
Table 5. Top 10 journals in terms of centrality on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the journal.
Table 5. Top 10 journals in terms of centrality on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term in the journal.
JournalPublicationsCentralityYear
Acta Oecologica310.042014
Soil Biology and Biochemistry30620.032014
Geoderma30520.032014
Journal of Statistical Software1470.032014
Earth System Science Data960.032015
Journal of Analytical and Applied Pyrolysis790.032014
Chinese Geographical Science760.032014
Advances in Agroecology610.032014
Quaternary Science Reviews600.032015
Biological Conservation580.032014
Table 6. Top 10 most-cited authors on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term for the author.
Table 6. Top 10 most-cited authors on soil organic carbon research from 2014 to 2023. “Year” represents the earliest publication year that used the term for the author.
RankAuthorCountryFrequencyCentralityYear
1Lal, RattanUSA12240.032014
2Six, JohanSWITZERLAND9030.042014
3Vance, Eric D.USA5080.032014
4Lehmann, JohannesUSA4690.022014
5Schmidt, Michael W. I.SWITZERLAND4590.012014
6Kuzyakov, YakovGERMANY4450.022014
7Walkley, AENGLAND4370.012014
8Cambardella, Cynthia A.USA3850.012014
9Jobbagy, Esteban G.USA3790.012014
10Davidson, Eric A.USA3770.042014
Table 7. Top 10 most-cited publications on soil organic carbon research from 2014 to 2023.
Table 7. Top 10 most-cited publications on soil organic carbon research from 2014 to 2023.
RankTitleReferenceCitationCentralityYearJournal
1Total carbon and nitrogen in the soils of the world[3]1360.052014EUR J SOIL SCI
2Soil organic carbon storage as a key function of soils—A review of drivers and indicators at various scales[5]1340.042019GEODERMA
3Conceptualizing soil organic matter into particulate and mineral-associated forms to address global change in the 21st century[9]1260.042020GLOBAL CHANGE BIOL
4Soil carbon 4 per mille[64]1080.032017GEODERMA
5Soil carbon storage informed by particulate and mineral-associated organic matter[65]1000.022019NAT GEOSCI
6The contentious nature of soil organic matter[66]870.12015NATURE
7Quantitative assessment of microbial necromass contribution to soil organic matter[67]820.042019GLOBAL CHANGE BIOL
8The importance of anabolism in microbial control over soil carbon storage[68]760.032017NAT MICROBIOL
9Persistence of soil organic matter as an ecosystem property[69]740.012011NATURE
10Calcium-mediated Stabilisation of soil organic carbon[70]680.032018BIOGEOCHEMISTRY
Table 8. Top 10 keywords on soil organic carbon research from 2014 to 2023.
Table 8. Top 10 keywords on soil organic carbon research from 2014 to 2023.
RankKey WordsFrequencyCentralityEarliest Publication Year
1soil organic carbon102902014
2matter10180.012014
3nitrogen92402014
4sequestration7530.012014
5organic carbon69102014
6dynamics68102014
7organic matter60902014
8management49302014
9microbial biomass4650.012014
10carbon4530.012014
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Fan, M.; Yang, W.; Wu, J.; Zhang, H.; Ye, Z.; Shaukat, M. Soil Organic Carbon Research and Hotspot Analysis Based on Web of Science: A Bibliometric Analysis in CiteSpace. Agriculture 2024, 14, 1774. https://doi.org/10.3390/agriculture14101774

AMA Style

Fan M, Yang W, Wu J, Zhang H, Ye Z, Shaukat M. Soil Organic Carbon Research and Hotspot Analysis Based on Web of Science: A Bibliometric Analysis in CiteSpace. Agriculture. 2024; 14(10):1774. https://doi.org/10.3390/agriculture14101774

Chicago/Turabian Style

Fan, Manman, Wenyan Yang, Jingtao Wu, Huan Zhang, Zhengwei Ye, and Muhammad Shaukat. 2024. "Soil Organic Carbon Research and Hotspot Analysis Based on Web of Science: A Bibliometric Analysis in CiteSpace" Agriculture 14, no. 10: 1774. https://doi.org/10.3390/agriculture14101774

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