# Towards smart soil carbon pool management of grassland: a bibliometric overview from past to future

Zhaoxia Jiang, Hongyuan Ma, Shaoyang Li, Congcong Zheng, Edith Bai

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Zhaoxia Jiang, Hongyuan Ma, Shaoyang Li, Congcong Zheng, Edith Bai. Towards smart soil carbon pool management of grassland: a bibliometric overview from past to future. Ecological Processes, 2025, 14, 10.1186/s13717-025-00620-1 . hal-05183784

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# Towards smart soil carbon pool management of grassland: a bibliometric overview from past to future

Zhaoxia Jiang<fnref n="1" />,<fnref n="2" />, Hongyuan Ma<fnref n="2" />*, Shaoyang Li<fnref n="2" />, Congcong Zheng<fnref n="3" /> and Edith Bai<fnref n="1" />*

**Abstract**

**Background** More than 90% of the carbon in grassland ecosystems is stored in the soil. Grassland land-use has been considered as a fundamental aspect altering soil carbon pool dynamics in the context of global change. However, a comprehensive understanding of the effects of different land-use practices on grassland soil carbon pools is lacking.

**Methods** Based on 2151 papers retrieved from the Web of Science database, we used bibliometric methods for the first time to summarize the research areas and trends of grassland soil carbon pools under various land uses.

**Results** Our results showed that (1) Management, sequestration, nitrogen, land-use, and dynamics were the most frequently occurring keywords. (2) Co-occurrence network analysis classified the keywords into three thematic clusters: (i) carbon and nitrogen coupling mechanisms regulating soil organic carbon (SOC) dynamics, (ii) microbial-mediated pathways linking management practices to SOC sequestration, (iii) cascading climate-vegetation-SOC. (3) Thematically, the hot topics shifted from focusing on the relationship between grassland biomass and SOC at broad geographic scales to gradually emphasizing the mechanisms of soil microbial influence on SOC, and from focusing on the effects of nitrogen deposition to focusing on the effects of global climate change on SOC. (4) We further summarize the trends of SOC pool changes under different land-use. Establishing multi-pool management to optimize soil carbon sequestration may be the key to sustainable grassland ecosystem development.

**Conclusions** This study summarizes the research progress and future hotspots of grassland soil carbon pools under diverse land use patterns, which can help to improve the carbon sequestration potential and mitigate the effect of climate change. Better integration of molecular and ecosystem experimentation with mathematical modeling is essential for future smart management of grassland SOC pool.

**Keywords** Carbon sequestration, Grassland, Land use, Soil organic carbon, Bibliometric analysis

**Introduction**

As the largest reservoir of organic carbon in terrestrial ecosystems, soils store most of the Earth's carbon. It has been estimated that for every 10% increase in the soil carbon pool, there is a potential reduction of at least 20% in the atmospheric CO₂ concentration (Kell 2012; Camenzind et al. 2023). Under ideal conditions, an additional 2–5 Pg CO₂ can be sequestered per year with the global soil organic carbon (SOC) sequestration technologies (Bossio et al. 2020). Soil carbon sequestration was regarded officially as an effective measure to mitigate

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<footnote>*Correspondence:
Hongyuan Ma
mahongyuan@iga.ac.cn
Edith Bai
baie612@nenu.edu.cn</footnote>

<footnote n="1">¹ Key Laboratory of Geographical Processes and Ecological Security of Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Changchun 130024, China</footnote>

<footnote n="2">² State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, Jilin, China</footnote>

<footnote n="3">³ INRAE, UMR ISPA, 33140 Villenave d'Ornon, France</footnote>
climate change at the 2015 United Nations Climate Change Conference. Grassland ecosystems cover approximately 40% of the Earth's land surface (Scurlock and Hall 2002; Liu et al. 2023b), play an important role in the terrestrial carbon cycle, and are characterized by large inter-annual variability in biomass and high sensitivity to climate change and human activities (Ahlström et al. 2015; Sun et al. 2020). To mitigate the negative effects of global CO₂ concentration and temperature increase, improving carbon sequestration through grassland management is regarded as an important way, and it is also crucial for achieving carbon neutrality.

Grasslands contain approximately 525 Pg C, which accounts for 16% to 19% of the total organic carbon in terrestrial ecosystems. This makes grasslands the second largest carbon sequestering ecosystem and plays a significant role in the global carbon cycle (Ochoa-Hueso et al. 2018; Bai et al. 2020; Peng et al. 2023). Over 90% of the carbon in grassland ecosystems is distributed in soil (Xiao et al. 2009). The carbon sequestration capacity of soils depends on the balance between carbon input and output (Davidson and Janssens 2006; Yigini and Panagos 2016). Meanwhile, the distribution of grasslands in arid and semi-arid climatic zones makes them highly sensitive to climate change, leading to significant interannual fluctuations in their carbon sinks that are greatly impacted by global change (Peng et al. 2023). The interannual variability of carbon sinks in arid and semi-arid ecosystems accounts for 39% of the global interannual variability of terrestrial carbon sinks (Ahlström et al. 2015). In the context of global change, such as human activities induced land-use has been demonstrated to result in a substantial decline in soil carbon pools. Carbon emissions due to land use change account for about 25% of global CO₂ emissions (Hong et al. 2021). From 2010 to 2019, terrestrial ecosystems emitted an average of 1.6 Pg C into the atmosphere per year due to land use change (Global carbon budget 2020). It is important to note that this carbon loss can be mitigated through proper management practices (Zhao et al. 2023).

As the main form of human disturbance activities, land-use change such as grazing and tillage are usually regarded as key factors affecting carbon stocks in grassland (Vannucchi et al. 2015). Excessive or irrational use of grasslands including heavy grazing and tillage can lead to soil degradation, negatively impacting soil carbon fixation (Wang et al. 2008). Land use change has a significant impact on particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), which are regarded as the key components of SOC (Zhou et al. 2006; Song et al. 2018). It has been demonstrated that different utilization patterns and durations of grasslands can significantly alter soil carbon pools and nutrient

dynamics at both local and global scales. Tillage and mowing significantly increase belowground net primary productivity and carbon allocation (Diabate et al. 2018), while overgrazing degrades grasslands, threatening their biodiversity and function (Bardgett et al. 2021). A grazing exclusion and enclosure practice has significantly increased soil carbon sequestration, promoted nutrient cycling in soil aggregates and altered the composition of related microbial functional genes. Meantime, long-term grazing exclusion has been found to have the opposite effect, causing a decrease in the carbon sequestration potential of grasslands (Ju et al. 2023). The pathways through which different grassland land use practices affect soil carbon pools are diverse and complex, resulting from the interaction of many factors. To maximize the carbon sequestration capacity of grassland ecosystems, it is essential to strengthen research on soil carbon pools in grasslands with different land-use patterns.

As an effective tool to describe the state of knowledge, characteristics and trends in a given discipline, bibliometric analysis is increasingly being used for research assessment due to its advantages in combining database management, statistics, and computer engineering (Aria and Cuccurullo 2017). It involves qualitative and quantitative analysis of publications indexed by databases based on statistics and computing technology, which makes the outputs more objective and reliable (van Eck and Waltman 2014; Liu et al. 2021). In this study, we pioneered the application of bibliometric methods to comprehensively analyze the grassland carbon pool under different land use management. Through a systematic mining and objective quantification of extensive literature data, we have uncovered the development of research hotspots, interdisciplinary patterns, and latent research gaps that traditional reviews have been unable to adequately identify. The bibliometric methods also can overcome the limitations of conventional meta-analyses, which have been criticized for their narrow focus on statistical merging and lack of in-depth exploration of literature's external features and knowledge-based networks. The objectives of this study include: (a) analyzing global research patterns on grassland soil carbon pools under different land use practices, (b) providing a comprehensive overview of the scientific output on this topic over time and space, and (c) identifying potential future research trends and hotspots.

## Materials and methods

### Data sources

For the data retrieval, bibliometric data collection was carried out on 26 February 2024, within the expanse of the Science Citation Index-Expanded (SCI-E) database, encompassed by the "Web of Science Core Collection"
(http://www.webofknowledge.com). Publications were further searched with the following search command: ("carbon store OR carbon stock OR carbon storage OR carbon sequestration OR carbon pool OR storing carbon") AND ("grassland OR prairie OR steppe OR savanna OR savannah OR meadow") AND ("management OR land-use OR practice OR land-cover change") AND ("soil OR soils OR land"). The Boolean operators "AND" and "OR" were judiciously employed to maximize the precision of our paper selection process. Specifically, "AND" was deployed to ensure the comprehensive inclusion of research related to all facets of carbon sequestration and grassland management, while "OR" facilitated the search for any one of the specified terms. Consequently, a total of 2,159 publications were garnered, spanning across all years of publication until 2024. From this database, 2,151 publications were meticulously curated to ensure the integration of essential elements such as title, authors, keywords, ISO source abbreviation, abstract, publication year, volume, and issue. A more detailed breakdown of these criteria can be found in Table 1.

## Data analysis and statistics

The data were extracted, and then transformed into Bib TeX format, ready to undergo comprehensive bibliometric analyses, executed utilizing the R software, and specifically, the Bibliometric package. To conduct a thorough examination of relevant research outputs, their decadal evolution, and emerging hotspots, we analyzed (a) the number of publications; (b) the quantification of scientific productions on both a national and institutional levels. To gain deeper insights into the distribution of the output in different journals, both paper numbers, total citation, and h-index were carried out in our analysis. The

h-index of the journal was used as an indicator of citation and the impact of publications for the parameters related to journals, as it could measure both the productivity and citation impact of the publications. It is worth noting that the h-index was derived exclusively from citations sourced from the WoS Core Collection (Hirsch 2005; Oliveira Filho and Pereira 2020).

To further investigate the evolving trends and advances within the sphere of our chosen subject, we undertook a comprehensive analysis encompassing keyword frequency and relationship exploration. This multifaceted analysis was facilitated through the deployment of word cloud and co-occurrence analyses. The word cloud was used to show the frequency of the 50 most common keywords on carbon sequestration and grassland management research over the past 30 years. Furthermore, we constructed a network of keyword co-occurrence, employing the 50 most prominent keywords, to elucidate the current research focal points in the realms of carbon sequestration and grassland management. Within this network, variations in circle sizes are indicative of the frequency of keyword appearances within a given cluster. Distinct colors denote separate clusters, signifying that these keywords are more likely to co-occur in the same scholarly publication. The thickness of connection lines between two circles reflects the strength of the relationship between the respective keywords. Thicker lines signify a more robust association.

To better understand the temporal evolution of research topics, we executed a temporal trend analysis of keywords. Besides, by applying a clustering algorithm to a keyword network, we were able to accentuate particular themes within the field. This analysis primarily focused on two themes: basic and motor themes. Basic themes encompass fundamental concepts of crucial importance in the field, thought they are not yet fully developed. On the other hand, motor themes denote topics that are both highly significant and in a well-developed state (Cobo et al. 2011; Zheng et al. 2023). It is imperative to highlight that all bibliometric analyses, data processing, and figure generation were meticulously executed using R 4.0.4 and Origin 2018 software.

<table><caption>**Table 1** Main information on studies of grassland soil carbon pools of different land-use</caption><thead><tr><td>Description</td><td>Data</td></tr></thead><tbody><tr><td>Time span</td><td>1991–2024</td></tr><tr><td>Sources (Journals, Books, etc.)</td><td>359</td></tr><tr><td>Publications</td><td>2151</td></tr><tr><td>Annual growth rate (%)</td><td>11.74</td></tr><tr><td>Author's Keywords (DE)</td><td>5313</td></tr><tr><td>Authors</td><td>7112</td></tr><tr><td>Average years from publication</td><td>7.67</td></tr><tr><td>Average citations per publication</td><td>43.83</td></tr><tr><td>Single-authored docs</td><td>54</td></tr><tr><td>Authors per publication</td><td>5.23</td></tr><tr><td>International co-authorships (%)</td><td>34.91</td></tr><tr><td>Affiliation</td><td>2558</td></tr></tbody></table>

## Results

### Variations in publication number and representative papers

#### Trends of the publications over time

As shown in Fig. 1, the first paper was published in 1991. There is an overall increasing trend in the number of publications from 1991 to 2023, with an average growth rate of 17.95% per year. The trajectory can be delineated into two developmental phases: the initial phase spanning from 1991 to 1999, characterized by a
<figure><img src="image_4.png" /><figcaption>**Fig. 1** Number of papers published per year from 1990 to 2023 and total publications on soil carbon pools in grasslands of different land-use types</figcaption></figure>

relatively low publication volume. During this period, only 15 relevant papers were published, which constituted 0.70% of the total papers retrieved from the database. In the second phase, from 2000 to 2023, 2,136 papers were published, accounting for 99.30% of the total papers retrieved from the database. As of February 26, 2024, a cumulative total of 94,283 citations have been accumulated by these publications.

Scientists began to pay attention to changes in soil carbon pools in grasslands with different land use from the 1990s. The paper titled "Effects of changing land use in the Netherlands on net carbon fixation" was published in the "Netherlands Journal of Agricultural Science" and authored by Wolf and Janssen. This paper enables the calculation of the new equilibrium state of the soil carbon pool and the change rate of the soil carbon pool size when land use changes occur across different ecosystems. This methodology proved particularly instrumental for analyzing the impacts of land use changes on soil carbon sequestration, particularly facilitating large-scale studies (Wolf and Janssen 1991).

**Most cited papers**

We have compiled the top 10 most cited papers. Among these 10 papers, nine are review papers, and one research paper uses isotope techniques to study the decomposition rates of soil organic matter (Table 2). The most cited paper is "The vertical distribution of soil organic carbon and its relation to climate and vegetation" published in the journal of "Ecological Applications" by Jobbagy and Jackson from Duke University in 2000, which was cited 3,451 times, and this seminal work was based on analysis of a global soil dataset (Jobbagy and Jackson 2000). This paper reveals that the vegetation type serves as the primary factor in controlling the vertical distribution of SOC, thus highlighting the importance of vegetation change for soil carbon dynamics.

The second most cited paper was "Calculation of organic matter and nutrients stored in soils under contrasting management regimes". In this paper, the authors emphasize that when assessing changes in SOC and nutrient storage induced by management regimes, the compared soil qualities must be equivalent. Calculation
<table><caption>**Table 2** The 10 most cited scientific articles on the study of soil carbon pools in grasslands of different management types during the period 1990–2024</caption><thead><tr><th>Article title</th><th>Years of publication</th><th>Journal</th><th>Average citations per year</th><th>Total citations</th></tr></thead><tbody><tr><td>The vertical distribution of soil organic carbon and its relation to climate and vegetation</td><td>2000</td><td>Ecological Applications</td><td>138.0</td><td>3451</td></tr><tr><td>Soil carbon sequestration and land-use change: processes and potential</td><td>2000</td><td>Global Change Biology</td><td>73.5</td><td>1837</td></tr><tr><td>Calculation of organic matter and nutrients stored in soils under contrasting management regimes</td><td>1995</td><td>Canadian Journal of Soil Science</td><td>37.6</td><td>1129</td></tr><tr><td>Grassland management and conversion into grassland: effects on soil carbon</td><td>2001</td><td>Ecological Applications</td><td>40.2</td><td>965</td></tr><tr><td>Trading water for carbon with biological carbon sequestration</td><td>2005</td><td>Science</td><td>45.4</td><td>908</td></tr><tr><td>Climatic, edaphic, and biotic controls over storage and turnover of carbon in soils</td><td>1994</td><td>Global Biogeochemical Cycles</td><td>25.4</td><td>788</td></tr><tr><td>Climate change mitigation of global land suitability for clean development mechanism afforestation and reforestation</td><td>2008</td><td>Agriculture, Ecosystems and Environment</td><td>42.6</td><td>725</td></tr><tr><td>Carbon sequestration in the agricultural soils of Europe</td><td>2004</td><td>Geoderma</td><td>29.7</td><td>623</td></tr><tr><td>Management options for reducing CO<sub>2</sub> emissions from agricultural soils</td><td>2000</td><td>Biogeochemistry</td><td>23.7</td><td>592</td></tr><tr><td>Land-use conversion and changing soil carbon stocks in China's 'Grain-for-Green' Program: a synthesis</td><td>2014</td><td>Global Change Biology</td><td>48.0</td><td>528</td></tr></tbody></table>

<figure><img src="image_5.png" /><figcaption>**Fig. 2** The top 50 keywords represented by the word cloud. Each label is a single word, and the font size indicates its frequency</figcaption></figure>

of carbon and nitrogen content in soils requires consideration of soil depth and bulk density to accurately estimate the quantity of elements per unit area (Ellert and Bettany 1995). This has enhanced the accuracy of estimates of SOC reservoirs and attracted scientific attention.

## Research topics and temporal evolution of keyword frequencies

### Most popular keywords

We used the word cloud to identify the 50 most common keywords in this topic over the past 30 years. As shown in

Fig. 2, "management", "sequestration", "grassland", "land-use", "carbon sequestration", and "land-use change" are the most frequently occurring keywords. These terms are directly relevant to our research topic and are commonly used in related papers. Additionally, the word cloud reveals the prevalence of high-frequency keywords such as "nitrogen" (449 times, 5.63% of total keywords), "dynamic" (341, 4.27%), and "climate-change" in the corpus. This shows that research on soil carbon pools under different land-use patterns is still closely related to nitrogen deposition, climate change, and carbon sequestration.

We further categorize these keywords into four aspects. The first area focuses on the decomposition and transformation processes of SOC. The second part is the influence of biological factors on SOC turnover. The third group of keywords is the abiotic factors that affect the decomposition of SOC, mainly including "nitrogen", "climate change", "climate". The last keyword grouping pertains to regions, including "China", "Loess Plateau", and "Inner Mongolia".

Over the past 30 years, research on soil carbon pools in grasslands under different land uses has undergone an evolution in keywords. From 1991 to 2000, research primarily focused on regional-scale grassland ecosystems, including climate change, nitrogen deposition, and grassland biomass. From 2001 to 2010, research on regional-scale grasslands shifted to organic matter transformation
kinetics, land management practices, increased nitrogen deposition, and began to focus on the effects of grassland conversion to cropland on SOC. There has been a shift in research focus from regional-scale grassland SOC storage to carbon fluxes. From 2011 to 2017, scientists focused on the impacts of different management and land-use on SOC sequestration under global climate change. Over the past 20 years, scientists have conducted in-depth studies on "nitrogen", with research interest gradually cooling in recent years. Between 2018 and 2024, research efforts have persistently centered on the impacts of land-use patterns on the carbon reserves within grassland soil and their mineralization rates under the backdrop of climate change (Fig. 3). This is because most grassland ecosystems are in arid and semi-arid regions, and their biomass and soil carbon reserves are sensitive to climate factors (Ahlström et al. 2015; Maurer et al. 2020). In addition, the global drylands have continued to expand and the severity of droughts has increased in recent decades, with future global climate change expected to continue and intensify (Tariq et al. 2024).

## Co-occurrence network of popular keywords

The co-occurrence network of hotspot keywords reveals the most prominent research questions in the field. The network displays three clusters, as follows: the red cluster focuses on the coupling of carbon and nitrogen in grassland SOC pools under different land uses, the blue cluster focuses on the mechanisms of soil microbial effects on SOC mineralization and fixation in

grassland under different land uses, and the green cluster is mainly about the impact of climate change and aboveground vegetation biomass on SOC in grassland under different land uses (Fig. 4).

## Marked countries, dominant institutes and journals

### Marked countries

Statistical analysis reveals that these papers were collectively published from 80 countries, with the majority concentrated in 15 countries. 1815 papers (86.05% of the total) were published in these countries. The top five countries in terms of publication volume are China (678, 31.5%), the United States (388, 18.04%), Germany (127, 5.9%), the United Kingdom (103, 4.78%), and France (81, 3.77%). The United States, France, and the United Kingdom published their first papers in 1994, while Germany and China published their first papers in 2000 and 2001, respectively (Table 3). Since 2002, the number of annual publications in the United States has risen steadily. It was consistently the world's leading country in terms of publication volume until 2018, when it was overtaken by China.

The United States (29,295), China (19,170), and Germany (7,363) rank as the top three countries in terms of total citations received by their publications, with the United Kingdom (103) and France (81) ranking fourth and fifth, respectively. China leads in terms of output, but ranks second in total citations received, with an average of 28.3 citations per paper (Table 3).

<figure><img src="image_6.png" /><figcaption>**Fig. 3** Thematic evolution of popular keywords in the study of soil carbon pools of grasslands under different utilization types. The horizontal axis represents time periods, with boxes of different colors representing different keywords. The size of each box represents the keyword frequency in different time periods, while lines connecting boxes illustrate their temporal evolution, transfer, and inheritance</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Fig. 4** Co-occurrence network of top 50 keywords. The size of the circle and the connecting lines represent the keyword frequency and the relationship respectively. The larger the size of the circle, the higher the frequency. Similarly, the thicker the line, the stronger the relationship between keywords. Different colors represent different clusters, indicating that these keywords appear more frequently in the same publication. Red cluster, the coupling of carbon and nitrogen in grassland SOC pools under different land use; blue cluster, the mechanisms of soil microbial effects on SOC mineralization and fixation in grassland under different land use; green cluster, the impact of climate change and aboveground plant biomass on SOC in grassland under different land use</figcaption></figure>

## Marked institutions

A total of 2,558 institutions globally have conducted research on changes in grassland soil carbon pools under different land use practices. The top fifteen most productive institutions contributed 58.9% (1,267 papers) of the total publications. University of Chinese Academy of Sciences (155, China) ranked first in terms of the highest number of publications, followed by Northwest A&F University (151, China), Beijing Normal University (143, China), Institute of Geographical Sciences and Natural Resources Research (116, China), and Chinese Academy of Sciences (100, China). This distribution aligns with the ranking of countries with the highest productivity and most citations. Among the top 15 institutions, nine

are from China, three from the United States, and one each from Germany, Canada, and the United Kingdom (Table 4). In recent years, the number of relevant papers published by Chinese institutions has increased annually, playing an increasingly significant role in this field.

## Marked journals

Research papers on this topic have been published in 359 journals. The top five journals by publication volume are *Agriculture, Ecosystems & Environment*, *Science of the Total Environment*, *Global Change Biology*, *Catena*, and *Geoderma*. *Agriculture, Ecosystems & Environment* has published 104 papers (5%, h-index = 41), *Science of the Total Environment* has published
<table><caption>**Table 3** The fifteen most productive and most cited countries in terms of research on soil carbon pools in grasslands of different management types</caption><thead><tr><th colspan="2">Country production</th><th colspan="4">Most cited countries</th></tr><tr><th>Ranks</th><th>Country</th><th>Number of papers</th><th>Country</th><th>Total citations</th><th>Average article citations</th></tr></thead><tbody><tr><td>1</td><td>China</td><td>678</td><td>USA</td><td>29295</td><td>75.5</td></tr><tr><td>2</td><td>USA</td><td>388</td><td>China</td><td>19170</td><td>28.3</td></tr><tr><td>3</td><td>Germany</td><td>127</td><td>Germany</td><td>7363</td><td>58.0</td></tr><tr><td>4</td><td>United Kingdom</td><td>103</td><td>United Kingdom</td><td>6756</td><td>65.6</td></tr><tr><td>5</td><td>France</td><td>81</td><td>France</td><td>4517</td><td>55.8</td></tr><tr><td>6</td><td>Brazil</td><td>71</td><td>Australia</td><td>3076</td><td>50.4</td></tr><tr><td>7</td><td>Australia</td><td>61</td><td>Canada</td><td>2894</td><td>48.2</td></tr><tr><td>8</td><td>Canada</td><td>60</td><td>Switzerland</td><td>2641</td><td>62.9</td></tr><tr><td>9</td><td>Italy</td><td>54</td><td>Italy</td><td>2235</td><td>41.4</td></tr><tr><td>10</td><td>Switzerland</td><td>42</td><td>Ireland</td><td>1868</td><td>60.3</td></tr><tr><td>11</td><td>India</td><td>35</td><td>Brazil</td><td>1787</td><td>25.2</td></tr><tr><td>12</td><td>Ireland</td><td>31</td><td>Netherlands</td><td>1465</td><td>47.3</td></tr><tr><td>13</td><td>Netherlands</td><td>31</td><td>Kenya</td><td>1144</td><td>163.4</td></tr><tr><td>14</td><td>Spain</td><td>27</td><td>India</td><td>943</td><td>26.2</td></tr><tr><td>15</td><td>Argentina</td><td>25</td><td>Argentina</td><td>886</td><td>35.4</td></tr></tbody></table>

<table><caption>**Table 4** The fifteen most productive affiliations in terms of research on soil carbon pools in grasslands under different land-use types</caption><thead><tr><th>Affiliation</th><th>Country</th><th>Articles</th><th>% total</th></tr></thead><tbody><tr><td>1</td><td>University of Chinese Academy of Sciences</td><td>China</td><td>155</td><td>7.21</td></tr><tr><td>2</td><td>Northwest A&amp;F University</td><td>China</td><td>151</td><td>7.02</td></tr><tr><td>3</td><td>Beijing Normal University</td><td>China</td><td>143</td><td>6.64</td></tr><tr><td>4</td><td>Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences</td><td>China</td><td>116</td><td>5.39</td></tr><tr><td>5</td><td>Chinese Academy of Sciences</td><td>China</td><td>100</td><td>1.94</td></tr><tr><td>6</td><td>Colorado State University</td><td>USA</td><td>94</td><td>4.37</td></tr><tr><td>7</td><td>Lanzhou University</td><td>China</td><td>71</td><td>3.30</td></tr><tr><td>8</td><td>Institute of Botany, Chinese Academy of Sciences</td><td>China</td><td>63</td><td>2.93</td></tr><tr><td>9</td><td>Michigan State University</td><td>USA</td><td>62</td><td>2.88</td></tr><tr><td>10</td><td>Institute of Soil and Water Conservation</td><td>China</td><td>58</td><td>2.70</td></tr><tr><td>11</td><td>Technical University of Munich</td><td>Germany</td><td>57</td><td>2.65</td></tr><tr><td>12</td><td>Peking University</td><td>China</td><td>55</td><td>2.56</td></tr><tr><td>13</td><td>University of Alberta</td><td>Canada</td><td>55</td><td>2.56</td></tr><tr><td>14</td><td>University of Aberdeen</td><td>Kingdom</td><td>53</td><td>2.46</td></tr><tr><td>15</td><td>University of Florida</td><td>USA</td><td>53</td><td>2.46</td></tr></tbody></table>

94 papers (4.8%, *h* = 30), *Global Change Biology* has published 80 papers (3.7%, *h* = 46), *Catena* has published 74 papers (3.4%, *h* = 23), and *Geoderma* has published 64 papers (3.0%, *h* = 32). It can be observed that the publications related to this topic are relatively dispersed across journals, with the top 10 journals publishing 642 papers, accounting for 29.85% of the total publications. 260 journals have published fewer than

5 papers, totaling 441 papers (20.50%). Among these journals, *Global Change Biology* has the highest number of citations, with 9,363 citations and published its first relevant article in 2000. The first relevant paper was indexed in *Plant and Soil* in 1994, while the other nine journals started to publish relevant papers after 2000 (Table 5). This pattern aligns with the development trend in the field of research on the effects of
<table><caption>**Table 5** Ten most cited sources for the research on soil carbon pools in grasslands of different land uses</caption><thead><tr><td></td><td>Sources</td><td>Articles</td><td>h-index</td><td>Total citation</td><td>PY start</td></tr></thead><tbody><tr><td>1</td><td>Agriculture, Ecosystems & Environment</td><td>104</td><td>41</td><td>6561</td><td>2002</td></tr><tr><td>2</td><td>Science of the Total Environment</td><td>94</td><td>30</td><td>3037</td><td>2002</td></tr><tr><td>3</td><td>Global Change Biology</td><td>80</td><td>46</td><td>9363</td><td>2000</td></tr><tr><td>4</td><td>Catena</td><td>74</td><td>23</td><td>1753</td><td>2011</td></tr><tr><td>5</td><td>Geoderma</td><td>64</td><td>32</td><td>4552</td><td>2004</td></tr><tr><td>6</td><td>Ecological Indicators</td><td>52</td><td>16</td><td>985</td><td>2012</td></tr><tr><td>7</td><td>Land Degradation & Development</td><td>50</td><td>22</td><td>1408</td><td>2005</td></tr><tr><td>8</td><td>Sustainability</td><td>42</td><td>12</td><td>449</td><td>2015</td></tr><tr><td>9</td><td>Journal of Environmental Management</td><td>41</td><td>14</td><td>806</td><td>2010</td></tr><tr><td>10</td><td>Plant and Soil</td><td>41</td><td>22</td><td>1807</td><td>1994</td></tr></tbody></table>

<table><caption>**Table 6** Top 10 high-frequency keywords in basic and motor themes of thematic analysis on soil carbon pools in grasslands of different land-use types</caption><thead><tr><td>Basic themes</td><td>Occurrences</td><td>Motor themes</td><td>Occurrences</td></tr></thead><tbody><tr><td>Sequestration</td><td>424</td><td>Management</td><td>471</td></tr><tr><td>Dynamics</td><td>341</td><td>Land-use</td><td>362</td></tr><tr><td>Storage</td><td>246</td><td>Grassland</td><td>350</td></tr><tr><td>Land-use change</td><td>234</td><td>Climate-change</td><td>242</td></tr><tr><td>Organic carbon</td><td>233</td><td>Vegetation</td><td>227</td></tr><tr><td>Matter</td><td>213</td><td>Biomass</td><td>173</td></tr><tr><td>Stocks</td><td>181</td><td>Carbon</td><td>171</td></tr><tr><td>Forest</td><td>173</td><td>Impacts</td><td>165</td></tr><tr><td>Climate</td><td>160</td><td>Diversity</td><td>130</td></tr><tr><td>Tillage</td><td>99</td><td>Productivity</td><td>122</td></tr></tbody></table>

different land-uses on soil carbon pool, with an increasing number of research papers published after 2000.

## Highlighted themes

We conducted a thematic analysis based on the keywords. Presently, research on plant biomass and carbon input under different grassland land-use practices under global climate change scenario has exhibited consistent and steady development. Motor themes such as "management", "land-use", "climate-change", "vegetation", and "biomass" are often involved. Studies on biodiversity and ecosystem productivity are expected to continue their stable development in the future. Research on the sequestration potential of grassland SOC pools under different land-uses will continue to be a key focus area in the future, and it has extremely promising prospects. These investigations offer a more comprehensive and in-depth understanding of the molecular mechanisms governing the dynamic alterations in the carbon storage of grassland soils. Basic themes such

as "sequestration", "storage", "dynamics", and "matter" are also frequently mentioned (Table 6).

## Discussion

Before 2000, the paucity of relevant papers can be attributed to the significant challenges of measuring large-scale ecosystems. These were caused by difficult measurements and limited technology. In the 1970s, international scholars began estimating the global carbon reservoirs in grassland ecosystems (Post et al. 1982; Houghton et al. 1983; King et al. 1997; Erb et al. 2017). After the 1990s, satellite remote sensing technology and global databases were refined, leading to further development in research on global grassland ecosystems and carbon reservoirs. This was achieved through the use of methodologies such as ecosystem flux monitoring, atmospheric monitoring and inversion, and model simulations to elucidate the dynamics of terrestrial ecosystem carbon sources and sinks (Fang et al. 2001). Consequently, scholarly publications on this topic gradually emerged. Since the beginning of the twenty-first century, propelled by technological advancements and the development of novel experimental methodologies, researchers have increasingly conducted field experiments and indoor cultivation trials (Tan et al. 2014). They are encouraged to conduct a more comprehensive study of the impacts of management practices on grassland soil carbon pools (Wang et al. 2023). This has led to a substantial increase in scientific publications. In the context of global climate change, the importance of soil carbon reservoirs has received growing attention. Consequently, research efforts aimed at improving soil carbon sequestration efficiency and increasing soil carbon storage have been intensified, driving the vigorous development of this research field (Canadell et al. 2011; Lavallee et al. 2024).

Different land use can influence soil moisture, nutrients, pH, microbial community diversity, and stability,
with long-term, unsustainable practices leading to soil
degradation, affecting the rate of soil carbon fixation
(Wang et al. 2008). The difference between carbon inputs
and outputs in ecosystems determines organic carbon
reserves, with organic carbon sources including plant-
derived carbon and microbial-derived carbon (Davidson
and Janssens 2006). The quantity and quality of SOC are
controlled by aboveground vegetation, which undergoes
biogeochemical transformations under the influence
of microorganisms and enzymes, with turnover times
ranging from days to hundreds of years (Kuramae et al.
2015). That explains the occurrence of keywords related
to vegetation, biomass, plants, and systems (Fig. 2). Many
scientists also focus on compositional changes during
SOC transformation processes, driven by soil micro-
bial growth and activity. Microorganisms play key roles
in controlling SOC transformations from two pathways:
promoting carbon release to the atmosphere through
decomposition metabolic activities and stabilizing car-
bon in less labile forms to prevent its release (Bardgett
et al. 2008; Schimel and Schaeffer 2012).

Additionally, keywords such as "model" and "pat-
terns" indicate that many studies employ model simula-
tions and data inversion to estimate grassland soil carbon
stocks (Wang et al. 2023). Molecular modeling has been
applied in the soil science for more than 20 years. How-
ever, owing to the extreme complexity and diversity of
soils, the extensive application of these models within the
realms of soil-related research remains restricted. Micro-
bial biomass directly affects the formation of microbial
sources of carbon, thus influencing the potential for car-
bon sequestration and organic carbon stocks. This find-
ing is in agreement with the previous research, which
highlights the importance role of microbial-derived
carbon in soils carbon storage under different soil man-
agement (Liang et al. 2017; Bai and Cotrufo 2022). The
greater the number of parameters introduced into the
soil carbon model for calibration during organic matter
transformation, the more precise the estimation of soil
carbon stocks.

Abiotic factors play a pivotal regulatory role in
the carbon cycling of grassland ecosystems (Austin
2011; Grunzweig et al. 2022). "Nitrogen" is the most
frequently occurring keyword, with carbon miner-
alization, decomposition, and storage constrained by
nitrogen levels. Nitrogen affects carbon loss processes,
such as litter decomposition and microbial respira-
tion, by altering microbial community composition and
functional attributes (Liu et al. 2023a). Therefore, many
ecologists are concerned about the impact of atmos-
pheric nitrogen deposition and nitrogen fertilization on
ecosystem productivity and carbon storage (Liu et
2023a). However, the effect of nitrogen applications

on soil carbon storage remains controversial, with
long-term nitrogen application may either increase or
decrease soil carbon storage. In the past two to three
decades, nitrogen deposition has been one of the most
frequently studied topics due to global climate change,
which also explains the occurrence of keywords such
as "climate change" and "CO2".

The prominence of "Inner Mongolia grassland", "Loess
Plateau" in the word cloud (Fig. 2) and the occurrence
of "Inner Mongolia Plateau" and "China" in the keyword
co-occurrence network graph (Fig. 4), along with China's
ranking as the second-highest country in terms of pub-
lished papers globally, can be attributed to the follow-
ing factors. China has abundant grassland resources,
which cover about 290 million hectares. Among them,
the Loess Plateau, Inner Mongolia Plateau and Qinghai-
Tibet Plateau are typical temperate grasslands or alpine
grasslands, making the ecological research conducted
in these areas highly representative (Xiao et al. 2009;
Peng et al. 2023; Wang 2023; Wang et al. 2023). Sec-
ondly, it is a result of changes in policy and advances in
research. Over the past thirty years, China's rapid eco-
nomic development has led to changes in the land-use of
many grasslands, resulting in the degradation of 70-90%
of grasslands in China and causing substantial SOC loss
(Li et al. 2004; Liu 2018). Since 1999, China has imple-
mented a series of large-scale vegetation restoration and
afforestation projects. These projects have played a sig-
nificant role in preventing land degradation, enhancing
biodiversity, and sequestering carbon (Yang et al. 2022).
Scientists have found that degraded grasslands have a
significant capacity to sequester carbon during the resto-
ration process.

Since the 1990s, many researchers have estimated
the vegetation and SOC stocks in Chinese grasslands.
Chinese scientists have mainly conducted analyses of
grassland carbon cycling through methods such as site
monitoring and transect survey, and quantitatively
evaluated the carbon pools and their dynamics in Chi-
nese grasslands. For instance, the Chinese Academy of
Sciences initiated the strategic priority research pro-
gram "Current status, rate, mechanism, and potential
of carbon sequestration in grassland ecosystems". The
objective of the project was to conduct surveys and col-
lected samples of grassland vegetation and soil across a
range of representative grassland types. To this end, field
stations and large-scale experimental platforms were uti-
lized. The findings of the study demonstrated that the
storage amount of SOC in Chinese grassland soil was
27.13 Pg C (Bai and Chen 2018). These efforts accurately
assess the current status and changes in carbon reserves
of Chinese grasslands, and to promote sustainable utili-
zation of grassland resources and ecological functions.
The red cluster focuses primarily on the variability of SOC sequestration processes and storage kinetics within grasslands under varying land-use management, given different nitrogen application rates or nitrogen deposition circumstances. As shown in Fig. 4, "nitrogen" and "sequestration" emerge as the most prominent keywords, consistent with the results shown in the word cloud. Keywords such as "climate", "organic carbon", "storage", and "dynamics" illustrate that nitrogen deposition exerts a significant influence on the global carbon cycle due to the complex interrelationship between the terrestrial carbon and nitrogen cycles (Vitousek 1994). Increasing the nitrogen content of the soil can alleviate nutrient limitations and thus promote soil microbial activity. Some studies have also found that the addition of nitrogen can slow the decomposition of organic matter by inhibiting the activity of lignin-degrading enzymes and lowering soil pH (Nazir et al. 2024).

In the blue cluster, the emphasis is placed on the specific response mechanisms of soil microbes regarding the mineralization and decomposition of SOC under different land use conditions (Fig. 4). Regardless of changes in grazing intensity, enclosure, or mowing frequency, SOC content is significantly influenced by microbial

community composition and activity. Certain specific bacteria and fungi and their functional groups exhibit linear changes during land-use transitions (Bai 2023). The response of microbial community composition and activity to grazing mainly depends on grazing intensity and duration, livestock size, and plant diversity. The expression of microbial functional genes associated with SOC, nitrogen, and phosphorus cycling is significantly influenced by livestock grazing. Presently, research on the mechanisms of soil microorganisms in SOC sequestration and the technologies for enhancing SOC sequestration by utilizing soil microorganisms have become hot topics.

The research in the green cluster indicates that researchers chiefly concentrate on the complex interactions among vegetation carbon sequestration ability, aboveground biomass, ecosystem productivity, and the impacts of climate change on SOC in grasslands (Fig. 4). Additionally, a subset of studies also explores the role of biodiversity and its conservation. This is attributable to the fact that alterations in land-use patterns predominantly affect composition and biomass of the aboveground vegetation, thereby having an indirect influence on SOC.

<figure><img src="image_8.png" /><figcaption>**Fig. 5** Trends of soil carbon pool in grasslands under different land-use types. SOC soil organic carbon, POC particulate organic carbon, MAOC mineral-associated organic carbon. The red line represents the trend of organic carbon sequestration in the grassland soil carbon pool with proper land-use management (such as rotational grazing, light grazing, seasonal grazing, timely mowing, zoned mowing, intermittent mowing, and stubble-retaining mowing). The green line, on the other hand, indicates the trend of organic carbon sequestration in the grassland soil carbon pool with improper land-use management (such as overgrazing and high-intensity mowing). Data sources for the SOC trend with different land-use refer to Appendix Table 1</figcaption></figure>
Considering that the main managements in grasslands
include grazing, tillage, grazing exclusion and mowing,
we have also made a comprehensive summary of the vari-
ation in the rate of soil organic carbon sequestration in
grasslands under long-term implementation of a single
management approach (Fig. 5). Proper land use, includ-
ing grazing exclusion, moderate grazing and mowing,
generally promotes the development of grassland eco-
systems by maintaining a stable plant community com-
position, enhancing species richness, and increasing the
activity of heterotrophic microorganisms. In contrast,
excessive land use, such as tillage, heavy grazing, and
frequent mowing, can reduce plant community com-
plexity, decrease plant productivity and soil microbial
diversity (Schönbach et al. 2010; Liu et al. 2018a; Yang
et al. 2012), and alter the physicochemical conditions of
microhabitats by affecting soil aggregates structure (Bai
et al. 2020; Bai and Cotrufo 2022; Hartmann and Six
2022). Compared to natural grassland, tillage soils exhibit
significantly increased bulk density, reduced stability of
soil aggregates, and alterations in the content of organic
carbon fractions, resulting in a significant decrease in
SOC content from 28 to 57% in different studies (Zhao
et al. 2011). With the lower clay content in the soil, the
physical protection of organic matter is weaker, SOC
losses are even more pronounced. Different from the
consistent carbon losses associated with arable farming,
the effects of grazing on soil carbon stocks vary with the
change of grazing intensity. Moderate grazing usually
can increase SOC stocks, while overgrazing may lead to
a decrease in SOC (Ren et al. 2024; Hao et al. 2024). The
evidence indicates that livestock grazing decreases SOC
stock, with an average reduction of 15% across five con-
tinents. The greatest reduction of 22% in SOC stock is
observed in the tropics, while the least reduction around
5% is observed in temperate grasslands (Bai and Cotrufo
2022). Even after grazing has ceased, legacy effects of
grazing can persist for many years, with primary pro-
ductivity and species richness in enclosed grasslands still
showing a declining pattern with increasing grazing his-
tory (Ren et al. 2024). Similar to grazing, many studies
have shown that rational mowing regimes are crucial for
nutrient cycling, sustainable utilization, and conserva-
tion of grassland ecosystems (Liu et al. 2018), but high-
intensity mowing significantly reduces the accumulation
of surface plant biomass and litter, leading to soil nutri-
ent loss, decreased total nitrogen contents, and limited
availability of substrates for soil microorganisms. Grazing
exclusion is a widely adopted restoration for degraded
grasslands; it enhances vegetation recovery by eliminat-
ing grazing pressure from large herbivores (Pulido et al.
2016). Appropriate enclosure duration can promote
plant growth, reduce soil mechanical disturbance, and

increases the abundance of C cycling-related genes in soil
macroaggregates, enhancing the potential of autotrophic
microorganisms to fix CO2, thereby increasing soil car-
bon pool (McSherry and Ritchie 2013). Conversely, some
studies argue that grazing exclusion may negatively affect
the health of grassland ecosystems and offset the direct
benefits of grassland restoration (McGovern et al. 2014;
Yu et al. 2015). The primary determinant of this phenom-
enon is the duration of grazing exclusion, since proper
exclusion duration can increase soil carbon and nutri-
ent cycling at local and global scales to varying degrees,
longer grazing exclusion can have negative impacts on
both SOC and local farmers' livelihoods (Zhang et al.
2022).

Accurate assessment of SOC stocks in grasslands under different land uses is currently severely limited. For instance: (1) The majority of soil carbon pool studies are conducted in the shallow layer (0–30 cm), while deep layer soil carbon pools are still less studied. (2) The research on multiple components of soil carbon is still not well understood. For example, POC and MAOC, which account for approximately 98% of SOC, showing different responses to climate change and alterations in land-use patterns. In substrates with relatively low SOC content, the carbon sequestration capacity is mainly attributed to MAOC. Conversely, when SOC approaches saturation, the potential for additional carbon storage depends on the accumulation of POC (Cotrufo et al. 2019). Without a comprehensive comprehension of the sub-pool dynamics, the reliability of model simulations regarding the soil carbon pool may be significantly compromised. Considering the possible differences in the mechanisms by which land-use patterns affect these two carbon pools, formulating a multi-pool management strategy for POC and MAOC under different land use conditions is a prudent approach to achieving intelligent management and accurate calculation of the grassland SOC pool (Angst et al. 2023).

Future perspective

Since 1900, the management of the grassland soil carbon
pool has evolved from its infancy to extensive manage-
ment and then to precision management. In the future,
smart management of the grassland soil carbon pool will
remain a focal area of research in ecology.

Future research in this field should focus on the follow-
ing aspects: Firstly, it is crucial to investigate the influ-
ence of the intensity of different utilization patterns on
carbon sequestration in grassland soils and to identify the
intensity thresholds specific to each pattern. Secondly, in
the context of global climate change, there is a need for
research to be conducted on the combined effects of mul-
tiple factors including climate factors, vegetation types,
and soil properties affecting soil carbon storage. Furthermore, the research should entail a thorough analysis of the formation mechanism of the spatial heterogeneity of grassland soil carbon storage. The objective is to achieve a precise estimation of the dynamic changes in grassland soil carbon storage for different grassland types (e.g. savannas, steppes and pampas) at different spatial scales. Finally, the integration of advanced technologies such as high-throughput sequencing, isotope labelling, long-term positional monitoring, model simulation, machine learning and big data analysis is imperative to simulate grassland soil carbon dynamics with greater accuracy over extended time scales, optimize SOC management strategies, and formulate sustainable and adaptive grassland utilization strategies.

## Conclusion

Through bibliometric analysis, we provide a comprehensive overview of research trends in grassland SOC pools under different land-use managements. Key findings indicate that the research direction has shifted from broad-scale studies focus on the relationship between biomass and SOC to detailed investigations of the molecular mechanisms of SOC sequestration in the context of climate change. Advanced technologies such as isotope labeling, high-throughput sequencing, and mathematical modeling, as well as effective multi-pool management, will continue to drive research on the carbon sequestration mechanisms of SOC at the microscale in the future. This study emphasizes the significance of different land-use patterns in enhancing grassland SOC sequestration and mitigating climate change, offering a roadmap for developing climate-smart agroecosystems and sustainable agricultural practices.

## Abbreviations

SOC Soil organic carbon

MAOC Mineral-associated organic carbon

POC Particulate organic carbon

## Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13717-025-00620-1.

Supplementary material 1: Table 1. Overview of Changes in Grassland Soil Carbon Pools under Different Land-use Patterns from Publication.

## Acknowledgements

We sincerely thank two anonymous reviewers for their helpful comments on this manuscript.

## Author contributions

Conceptualization, Zhaoxia Jiang, Congcong Zheng and Hongyuan Ma; methodology, Zhaoxia Jiang and Congcong Zheng; data acquisition, Zhaoxia Jiang; writing—original draft preparation, Zhaoxia Jiang, Congcong Zheng, Shaoyang Li; writing—review and editing, Hongyuan Ma, Congcong Zheng,

and Edith Bai; funding acquisition, Hongyuan Ma. All authors have read and agreed to the published version of the manuscript.

## Funding

This work was supported by the Joint Found of the National Natural Science Foundation of China (U23A2004), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA28110300), the national key research and development program (2022YFF1300601), the key research and development program of Jilin Province (20220203023SF), the Innovation Team Project of Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (2023CXTD02). C.C. Zheng was supported by the Joachim Herz Foundation (850035).

## Availability of data and materials

The data that support the findings of this study are available from the corresponding author upon reasonable request.

## Declarations

### Ethics approval and consent to participate

Not applicable.

### Consent for publication

All authors approved the manuscript for publication in ecological processes.

### Competing interests

No competing interest exists in this manuscript.

Received: 25 September 2024 Accepted: 28 April 2025

Published online: 21 May 2025

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