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Review

Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations

by
Yonglin Wu
,
Haitao Li
,
Xinran Liang
,
Ming Jiang
,
Siteng He
and
Yongmei He
*
College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(11), 1118; https://doi.org/10.3390/agriculture15111118
Submission received: 22 March 2025 / Revised: 15 May 2025 / Accepted: 20 May 2025 / Published: 22 May 2025
(This article belongs to the Topic Carbon and Nitrogen Cycling in Agro-Ecosystems and Other Anthropogenically Maintained Ecosystems—2nd Edition)
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Versions Notes

Abstract

:
Soil organic carbon (SOC) represents the most dynamic component of the soil carbon pool and is pivotal in the global carbon cycle. Global temperature rise and increasing drought severity are now indisputable realities, making soil organic carbon cycling under climate warming a critical research priority. This review elucidates the mechanism of the SOC response to temperature increase in terms of both extrinsic and intrinsic factors. The extrinsic factors are temperature elevation methods, rainfall, and land use. Different methods of temperature increase have their own unique advantages and disadvantages. Indoor warming methods exclude other factors, making temperature the only variable, but tend to ignore carbon inputs. In situ field warming and soil displacement methods help researchers explore the response of the complete ecosystem carbon cycle to temperature increase but cannot exclude the interference of factors such as rainfall. Elevated rainfall mitigates the adverse effects of elevated temperatures on organic carbon sequestration. In addition, the response of SOC to temperature elevations vary among different land use types. The temperature sensitivity of SOC is higher in peatland (high organic matter) alpine meadows (colder regions). The intrinsic factors that affect the response of SOC to elevated temperatures are SOC components, microorganisms, SOC temperature sensitivity, and SOC stability. The SOC decomposition rate is influenced by variations in the ratios of decomposable (easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC)) and stabilizing (inert organic carbon (IOC), alkyl carbon, and aromatic carbon) SOC to total organic carbon (TOC). Furthermore, temperature elevations also affect the soil microenvironment, resulting in microbial community reorganization such as changes in bacterial and fungal ratios and abundance. At the same time, soil aggregates, clay minerals, and iron and aluminum oxides protect the SOC, making it difficult to be utilized by microbial decomposition. The systematic clarification of the mechanism behind the SOC response to higher temperatures is crucial for accurately predicting and modeling global carbon cycles and effectively responding to the loss of SOC pools due to global temperature elevations.

Graphical Abstract

1. Introduction

The soil carbon pool is the largest carbon reservoir in terrestrial systems. Soil organic carbon (SOC) stores account for two-thirds of the terrestrial ecosystem carbon stocks, which is equivalent to twice the global atmospheric carbon stock and three times the vegetation carbon stock [1,2]. Over the past few years, terrestrial carbon sinks have absorbed about 3.61 Pg C year−1 from the atmosphere, accounting for 33.7% of total anthropogenic emissions from industrial activities and land use change [3]. SOC forms part of the soil carbon pool and plays an important role in the global carbon cycle [4]. According to the Sixth Assessment Report of the IPCC, human activities have increased the global mean surface temperature by approximately 1.1 °C from 2010 to 2019, with a projected increase of 4 °C in the 21st century. This escalation will promote microbial decomposition, increasing heterotrophic respiration in the soil and subsequent soil organic matter (SOM) degradation in the topsoil [5,6]. Global climate change profoundly affects the terrestrial carbon balance, especially SOC [7,8,9]. Elevated temperatures increase soil respiration rates. Prolonged temperature elevation durations and elevated temperatures increase carbon loss via soil respiration [10]. Temperature elevation conditions of 4 °C increase the CO2 emissions from the soil by 55%, which is partially attributed to soil heterotrophic respiration rather than autotrophy, resulting in an annual loss of 8.2 ± 4.2 tons of carbon per hectare from decomposing SOM [11].
Recent research has explored the mechanism behind the SOC response to increasing temperature. It is generally believed that higher temperatures increase the activity of soil microorganisms, consequently accelerating SOC decomposition. However, some studies indicate that higher temperatures may also increase the organic carbon content in soil [12,13]. The disparities in the research results are mainly attributed to the different temperature elevation conditions employed during experiments, the duration of temperature elevations, the soil type, and the local climate. Therefore, this paper assesses these differences to analyze the mechanisms behind the SOC response to elevated temperatures, including temperature sensitivity, turnover, and decomposition-related microorganisms and enzymes.

2. Extrinsic Factors Affecting the SOC Response to Elevated Temperatures

2.1. Variation in the SOC Response to Temperature Elevations in Different Temperature Elevation Methods

2.1.1. Indoor Temperature Elevations

The method of evaluating indoor temperatures elevations is to use a constant temperature incubator to cultivate soil at different temperatures (Figure 1a and Figure 2a). This method was employed to accurately control the extent of temperature elevation and processing time duration to elucidate the mechanisms underlying the SOC response to temperature elevations. Other factors were adjusted to ensure that the temperature was the sole variable and eliminate the influence of extraneous elements. Furthermore, indoor temperature elevations require less stringent instrumentation and facilitate easier equipment operation. Indoor temperature elevation experiments use temperature as the only variable, which is inherently more accurate. However, in actual natural environments, climatic temperature elevations occur as a gradual, fluctuating process. Extensive research on indoor temperature elevations has investigated the SOC decomposition process in elevated temperature conditions, often ignoring the fact that natural environmental temperature elevations accelerate microbial SOC decomposition and improve net primary productivity in plants, which enhances C output. This is a dynamic, complex process since the SOC content depends on the balance between the C output and inputs [14]. Thus, the conclusions of the indoor method tend to favor temperature elevations promoting SOC decomposition rather than accumulation. In addition, soil collection and treatment destroy the original soil aggregate structure, leading to bias in the experimental results. The soil C cycle response to rising temperatures occurs in distinct stages as the temperature elevation duration is extended [13], necessitating long-term temperature elevations experiments. However, existing studies have not conducted indoor temperature elevation experiments for a sufficiently extended duration, compromising the accuracy of the conclusions.

2.1.2. Field Temperature Elevations

Field temperature elevations are achieved by constructing external temperature elevation devices in the experimental area to simulate the effect of natural temperature elevations (Figure 1b and Figure 2b), which includes cable heating [13], infrared radiators [15], open-top assimilation tanks [16], and greenhouses [17]. Each temperature elevations method presents different advantages and disadvantages. For example, although infrared emitters are cost-effective, they display low heating efficiency [18], while using cables during heating may present a fire hazard [18], and open-top chambers display lower heating efficacy during cooler months [19]. Therefore, suitable temperature elevation equipment should be selected according to the climatic conditions in the experimental area. Unlike indoor temperature elevation methods, this technique preserves the soil structure and plants in the experimental areas, causing minimal disruption to the original ecosystem. In situ field temperature elevations methods facilitate the assessment of the carbon cycle responses of intact ecosystems to rising temperatures. Although in situ field temperature elevations are currently the most widely used method for assessing the impact of temperature, they have been unable to mitigate the influence of other factors in the field environment on SOC turnover, such as rainfall and atmospheric CO2.

2.1.3. Soil Displacement

Mountain temperatures increase significantly at lower altitudes, creating a vertical temperature gradient [20]. Changes in mountain temperatures in a global temperature elevation scenario can be projected by considering temperature escalation from high to low mountain elevations using a “space-for-time” model [21,22]. The effect of higher temperatures on SOC cycling was explored by transferring high-elevation soils to lower elevations (Figure 1c and Figure 2c) [23]. Although this method was cost- and labor-efficient since it did not require external equipment and control, transferring soil from high to low altitudes increased the temperature and altered the influence of factors such as rainfall and atmospheric CO2. Furthermore, the SOC stocks, as well as the above- and below-ground biomass carbon stocks, decreased significantly at lower altitudes [24]. The net ecosystem productivity displayed higher temperature sensitivity at high altitudes than at low elevations [25]. Warmer mountain temperatures accelerated SOC decomposition and emissions, leading to soil carbon loss [5]. Contrarily, the altitudinal gradient showed that the organic carbon content in the particulate state increased at a higher mountain altitude, while that in the mineral-bound state displayed no significant changes [26,27]. In addition, the aromatic and phenolic carbon concentrations in the SOC increased at higher altitudes, while that of alkyl carbon declined [28]. However, some studies have revealed lower alkyl carbon and higher alkoxyl carbon concentrations in high-altitude mountain soils [29], as well as an increase in the aromatic carbon concentration, which peaked in the middle of the altitude and then declined [30]. Transferring high-elevation soils to lower altitudes significantly increased the soil heterotrophic respiration, organic carbon decomposition, active microbial community components, and enzyme activities while decreasing the total SOC and growth rates [31,32].

2.2. Variation in the SOC Response to Temperature Elevations in Different Land Use

Variations in the soil texture, water content, organic matter content, and microbial community structures of different land use have resulted in divergent research results (Table 1). In humid subtropical soils, the SOC fractions in elevated temperature conditions primarily manifested as a decrease in labile O-alkyl C in carbohydrates [33]. The SOC in high-organic-matter soils was more sensitive to temperature elevations, showing a notable content increase of 13.3%, compared to the minimal changes in low-organic-matter soil [34]. Under the condition of rising temperature, the surface SOC in the alpine region increased, which is because the carbon input generated by net primary productivity of plants is greater than the carbon output generated by microbial activities. Conversely, a higher valley temperature accelerated the microbial decomposition rate and SOC loss in the surface layer [35]. The temperature sensitivity of SOC decomposition was higher in high-altitude areas with lower temperatures, indicating that the soil in colder areas was more responsive to global temperature elevations [36,37].

2.3. Variation in the SOC Response to Temperature Elevations in Different Rainfall Conditions

Variations were evident in the SOC response to higher temperatures in different rainfall conditions. This was attributed to changes in factors such as precipitation and temperature, possibly modifying the soil texture and plant and microbial growth, consequently altering the regional carbon inputs and outputs (Figure 3).
Lower precipitation intensified the impact of higher temperatures on vegetation, significantly decreasing the plant biomass and net carbon uptake by ecosystems. Additional precipitation failed to mitigate the negative effect of higher temperatures on plants [54]. Climate warming and lower precipitation exerted a superimposed effect on the SOC and dissolved organic carbon (DOC) and displayed a synergistic impact on MBC [55]. Furthermore, reduced precipitation counteracted the beneficial effect of temperature elevations on SOC by suppressing functional genes and unstable carbon supply in C-degrading fungi [56]. However, higher precipitation mitigated water loss and promoted microbial growth due to warmer atmospheric and soil temperatures [15]. The synergistic effect of higher temperature and precipitation resulted in a more pronounced SOC and MBC elevation compared to higher precipitation alone. These two conditions displayed a superimposed effect on SOC, DOC, and MBC [55]. Furthermore, elevated temperatures and rainfall significantly increased the below-ground plant biomass, the functional gene abundance of carbon-degrading bacteria, and the levels of certain DOCs, particulate organic carbons (POCs), and mineral-associated organic carbons (MAOCs) [56]. The SOC increment in response to increasing temperature also varied in different precipitation conditions, with parabolic change patterns in areas with average annual precipitation <1050 mm. Higher temperatures minimally affected the SOC increment in areas with average yearly precipitation >1050 mm [42]. Additionally, more significant MAOC and heavy fraction organic carbon (HFOC) loss was evident in the rainy season than during the dry season [57].

3. Intrinsic Factors Affecting the SOC Response to Elevated Temperatures

Elevated temperatures stimulated SOM decomposition, which reduced soil carbon stocks and promoted continuous greenhouse gas release from the soil, further exacerbating the greenhouse effect [58]. The terrestrial carbon cycle responded to elevated temperatures with substantial changes in the average global atmospheric CO2 growth rate, as well as ecosystem carbon loss due to lower vegetation productivity and increased soil respiration due to higher global temperatures [59]. The impact of temperature elevations on soil carbon pools primarily manifested as substrate limitation, microbial community adaptation (changes in microbial carbon utilization efficiency), or thermal enzyme activity compensation (the maximum potential activity decreased at higher temperatures) [60]. Elevated temperatures reduced the relative lignin abundance in the soil carbon pool, while microorganisms adapted to changes in the carbon pool to enhance carbon utilization efficiency [13]. Respiration by soil microbial communities is essential for carbon dioxide release from the soil carbon to the atmosphere.

3.1. The Effect of Temperature Elevations on SOC Fractions

Elevated temperatures changed the molecular composition of the SOC, promoted the preferential loss of plant organic matter, accelerated plant residue and microbial-derived fatty acid degradation, reduced aromatic compound deterioration, and induced structural changes in SOM composition, transitioning plant extracts to microbial extracts and transformants [61,62,63]. The impact of elevated temperatures on SOC components varied, significantly affecting MBC and displaying a minor positive influence on soil carbon sequestration enzyme activity while showing no impact on SOC functional groups [64]. Furthermore, elevated temperatures significantly decreased the EOC and MBC content in the soil while substantially increasing the DOC level [34]. Elevated temperature also substantially accelerated SOC decomposition, increased the cumulative CO2 emissions of the total organic carbon (TOC) in the soil, and promoted organic carbon decomposition, including inert organic carbon (IOC) and resistant organic carbon (ROC), consequently reducing their TOC proportion [57]. Prolonged temperature elevation reduced the effective phosphorus content in the soil, limiting microbial biomass biosynthesis and ultimately decreasing the microbial necromass carbon (MNC) level [65].
Elevated temperatures modified the chemical composition of SOC, decreasing the macroaggregate (2–0.25 mm) and microaggregate (0.25–0.053 mm) proportions and increasing the proportion of non-aggregated silt- and clay-sized fractions (<0.053 mm). Moreover, higher temperatures significantly decreased the POC, SOC, and phenolic SOC levels in the free microaggregates, while increasing the DOC and carboxylated SOC content. Elevated temperatures decomposed larger aggregates into smaller ones, hindering soil structure development. This decreased the proportion of large aggregates while increasing that of free microaggregates and chalk + clayey grain fractions, which reduced the SOC stability [66]. Due to its direct impact on crop root growth, elevated temperature also reduced the aromatic, carboxyl, and aryl carbons in the POM fractions of the free microaggregates [34]. Under temperature elevations conditions, the faster rate of microbial carbon decomposition in soils with lower carbon-to-nitrogen ratios allows for more rapid loss of organic carbon from the soil [67]. A higher C/N ratio slows down the promotion of SOC decomposition due to the increase of nitrogen content, which can reduce the ratio of fungi to bacteria and inhibit enzyme activity, thus reducing the rate of carbon decomposition [68]. The organic matter in low C/N soils is easier to decompose and promotes the activity of methanogenic bacteria, leading to an increase in methane emissions. Contrary to high C/N soils, it is more difficult to decompose organic matter in high C/N soil, and carbon dioxide emissions are dominant [53].

3.2. The Effect of Temperature Elevations on Soil Microorganisms and Enzymes

Microbial biomass and bacterial taxa represented the primary determinants in the carbon–climate feedback mechanism in the global temperature increase scenario, surpassing biochemical resistance, mineral protection, and substrate availability [69]. The sensitivity of microbial growth and respiration significantly influences the SOC response to elevated temperatures [33].
The carbon loss from the soil increased at the beginning of the temperature elevations period and decayed to a certain level within a few years as this process progressed. The microbial populations and degradative enzymes declined, while the reduced carbon content in the soil limited the microbial biomass associated with carbon decomposition. However, the physiological microbial characteristics changed at higher temperatures, possibly upregulating the carbon utilization efficiency while mitigating the microbial biomass decline and accelerating soil carbon loss. This further suggests that the response of soil carbon to elevated temperature depends on the carbon utilization efficiency of soil microbes [70]. Although short-term temperature elevations did not affect the soil microbial biomass, it altered the soil microbial community composition and reduced the abundance of bacteria, fungi, and actinomycetes. Organic carbon changes due to temperature elevations altered the microorganism membrane fatty acid fractions and mass, which included higher ratios of the cyclopropyl-to-monoallyl precursor fatty acids, saturated-to-monounsaturated fatty acids, and isomeric-to-trans-isomeric fatty acids [71]. In addition, fungal communities buffered the negative effect of temperature elevations on prokaryotes and caecilians by acting synergistically and increasing overall community resistance [72].
Short-term temperature elevations increased the number of Gram-positive bacteria and actinomycetes, while long-term temperature elevations elevated the fungal levels and reduced the number of actinomycetes [73]. Elevated temperatures increased the functional gene abundance in the microorganisms associated with refractory organic carbon decomposition [57,74]. Elevated temperatures increase the activity of enzymes involved in the decomposition of organic matter, leading to enhanced decomposition of the stabilized components of the SOC such as urease, cellulose hydrolase, Nacetylglucosaminidase, leucine aminopeptidase, β-glucosidase, phenol oxidase, peroxidase, and other enzymes [65,75,76]. Over time, this effect was attenuated by microbial acclimatization to temperature and the reduced substrate affinity for enzyme activity [77]. This decreased the number of soil fungi and microorganisms, as well as the activity of catabolic enzymes, such as β-glucosidase, due to higher temperatures [78].
The fungal community composition in high-latitude tundra ecosystems remained unchanged in elevated temperature conditions. However, a significant increase was evident in the relative abundance of the fungal genes involved in encoding vanillin dehydrogenase, invertase, and xylose reductase, which enhanced the carbon degradation capacity of the fungal community. However, changes in the fungal gene networks may alter fungal interactions, such as reducing the percentage of negative linkages and average clustering coefficients and increasing the average path distances [79]. Furthermore, higher temperatures more significantly affect the enzymes responsible for decomposing complex substrates (ligninase) than those involved in simple substrates (cellulase) degradation [80].
It is generally recognized that organic matter is a continuum of constantly decomposing organic compounds [81]. The response of the SOM to long-term climate change depended on the balance between inputs from plant litter and outputs from microbial decomposition [82,83]. Although the rate of soil carbon loss eventually declined in warmer soils as the substrate limitation increased, the time required remained unclear. It was also unclear whether long-term soil carbon balance was affected by plant–soil interactions or changes in soil microbial communities. In a high-plateau alpine environment, plant growth experienced low-temperature stress, while warmer temperatures enhanced plant photosynthetic capacity and below-ground biomass, alleviating the low-temperature limitations on plant growth [39,84,85]. Higher temperatures significantly affected the microbial biomass and community composition in alpine soil ecosystems [86,87], while minimally impacting the bacterial or fungal OUT (bacteriophage richness) in the soil. However, it promoted microbial growth and proliferation, which increased microbial source carbon (MRC) input [41]. Elevated temperatures increased oxidase activity in forest soils, which enhanced the ability of fungi to decompose organic carbon, stimulating carbon loss from the forest. Twenty microbial communities and enzyme activities responded to elevated soil temperatures. Temperature elevations significantly reduced the relative abundance of the total bacteria, G+ bacteria, G− bacteria, and 28 actinomycetes species. However, the relative abundance of soil fungi and oxidative enzyme activities increased significantly [23]. In summary, climate warming ultimately reduces soil organic carbon stability by altering soil organic carbon components, soil aggregates, microbial communities, and enzyme activities(Figure 4).

3.3. The Effect of Temperature Elevations on the Temperature Sensitivity of SOC Decomposition

The temperature sensitivity of SOC decomposition is regulated by several factors, including substrate availability [88], microbial activity inhibition [89], physicochemical protection [90], soil depth and elevation [91], climatic variations, and intrinsic C quality, with the greatest response to temperature changes exhibited in the intrinsic C quality [92]. Carbon quality–availability interactions generally control the temperature sensitivity of the mineralization (Q10) and depletion of high-quality SOC since higher temperatures significantly increase the SOC sensitivity to temperature elevations [93]. The decomposition of complex substrates with higher activation energies is more sensitive to temperature than that of simple substrates. The temperature sensitivity of SOC decomposition was significantly higher in the long-term carbon cycle than in the short-term cycle [10] and increased as the temperatures rose. The soil temperature’s sensitivity Q values were negatively correlated with SOC mass. A lower SOC mass increased the temperature sensitivity’s Q values [94]. Climate-induced changes in the chemical stability and physicochemical protection of SOC produce spatial heterogeneity in the temperature sensitivity of soil SOC decomposition [91]. The temperature sensitivity of soil SOC decomposition varies greatly in soil depth. The SOC of deep soil is more sensitive to temperature than that of topsoil [95]. Some studies contend that the susceptibility of SOC to higher temperatures is governed by biophysical stability processes rather than by the age of SOC or its chemical recalcitrance [96]. Stronger aggregate protection and lower microbial activity reduced the temperature sensitivity of SOC [97]. Below 25 °C, the SOC Q10 value of soil decreased noticeably at a higher incubation temperature [98]. The Q10 value of the easily decomposable SOC exceeded that of the stable SOC. This indicated that the stable SOC was more sensitive to higher temperatures than the easily decomposable SOC [99,100].

3.4. The Effect of Temperature Elevations on SOC Turnover

SOC consists of many compounds displaying different turnover behaviors and persistence. The turnover time of soil SOC is a key parameter in the carbon cycle model when predicting global carbon storage, providing a basis for estimating the response of soil to higher temperatures [101]. The factors affecting the turnover time of soil SOC include plant growth, soil microbial activity, soil temperature and humidity, soil chemical properties, soil matrix quality, and climate change, among which temperature is an important driving factor of soil SOC turnover time [102,103]. It is generally believed that a temperature increase accelerates the turnover of organic carbon in surface soil by enhancing the respiration of soil microorganisms [104]. However, some researchers have found that short-term temperature elevations reduce the temperature sensitivity of soil microbial respiration, resulting in slow turnover of SOC in grassland [105].
SOC mineralization increased at lower altitudes and at a higher average annual temperature. At a higher altitude, the sensitivity of SOC mineralization displayed a noticeable decline at higher temperatures. Furthermore, the response of SOC mineralization to elevated temperatures may change over time [71]. This response was mainly influenced by the soil chemical composition, with a higher soil active carbon component (O-alkyl C) increasing the SOC mineralization rate. High alkyl C levels in the soil and weak mineral protection (high energy density and low mass loss ratio during pyrolysis) increased the soil SOC susceptibility to a rise in temperature [106]. However, this sensitivity decreased as the clay minerals and total oxides in the soil increased. The closed environment inside the aggregate protected the SOM, restricting decomposition by microorganisms. This indicated that mineral protection reduced the SOC response to higher temperatures [107].

3.5. The Effect of Temperature Elevations on SOC Stability

SOC stability is mainly related to autochthonous refractory degradability, physical protection, chemical protection, and microbial activity (Figure 5). Microorganisms decomposed the carbohydrates in the soil, while the remainder consisted of hard-to-decompose IOCs. Therefore, the proportion of IOCs in the TOC could be used to evaluate SOC stability. The decomposition of alkyl carbon and aromatic carbon and their utilization by microorganisms were challenging, representing more stable organic carbon components. Alkoxy carbon and carboxy carbon were more easily decomposed and utilized by microorganisms, denoting unstable active organic carbon components. Therefore, the SOC stability could be assessed according to the lignin, alkyl carbon, and aromatic carbon content [108]. The soil aggregates displayed a certain encapsulation effect on the organic carbon. The organic carbon was partially combined with the soil aggregates to form particulate organic carbon, which was protected from microbial decomposition via environmental occlusion inside the aggregates [107]. In addition, clay minerals, iron, and aluminum oxides in the soil partially combined with the organic carbon to form mineral-bound organic carbon via ligand exchange, hydrogen bonding, cationic bonding bridges, and Van der Waals forces, which increased decomposition difficulty and utilization by microorganisms [109]. The POCs were more susceptible to microbial decomposition than mineral-bound organic carbon since they were not enclosed by micropores and microagglomerates or bound to mineral surfaces [110]. In cold regions, POCs dominated or co-dominated the SOC, increasing vulnerability to temperature elevations in cold regions [111].
SOC stability is closely associated with microbial metabolic activity. Although microorganisms are involved in the decomposition of plant-derived carbon, they are also immobilized in the soil in the form of microbial residues, which promotes microbial-derived carbon stability [112]. At elevated temperatures, the microbial biomass in the soil decreased as the unstable carbon pool in the soil was depleted, causing microbial community reorganization and a decline in the related SOC. As the temperature increased, the microbial community was continuously depauperated, increasing the homogeneity and fungal diversity while decreasing the microbial biomass, fungal dominance, and fungal/bacterial ratio [13]. Higher temperatures also changed the physiological microbial characteristics, which upregulated carbon utilization efficiency and accelerated soil carbon loss, suggesting that SOC stability depended on the soil microbial efficacy in utilizing carbon [70].

4. Conclusions

Global temperature elevations and drought conditions are accelerating the depletion of SOC pools, which increases atmospheric carbon dioxide and global temperature elevations. The effect of elevated temperatures on SOC is complex, decreasing the proportion of the difficult-to-decompose fraction while increasing the unstable SOC fraction. At higher temperatures, the SOC content decreases in macroagglomerates, while increasing in free microagglomerates. Furthermore, elevated temperatures also increase SOC turnover rates and temperature sensitivity and alter soil microbial community composition. This promotes further microbial decomposition of difficult-to-degrade SOC, which reduces SOC stability. Currently, there are limitations at both the spatial and temporal scales regarding the investigation of SOC response to temperature elevation. At the spatial scale, variation in the soil type and rainfall in different geographical locations can influence the response of SOC to higher temperatures. At the temporal scale, the time duration of the temperature increase changes the SOC component ratio, microbial community, and microbial carbon utilization efficiency. Therefore, the SOC response to temperature elevations occurred in different stages. To systematically and comprehensively clarify the mechanism underlying the SOC response to temperature elevations, it is necessary to establish global experimental stations and perform long-term field observations. Moreover, different heating processes exhibit distinct advantages and drawbacks, contributing to the discrepancies in various research conclusions. Due to technological limitations, the temperature elevation focus is currently restricted to the topsoil, with minimal research available on deep soils. Therefore, it is essential to address the impact of both temperature elevation and the comprehensive reaction of the entire ecosystem on SOC, including soil fauna and soil microorganisms.

Funding

This work was supported by the Key agricultural joint projects in Yunnan province (No. 202301BD070001-014), the National Natural Science Foundation of China (No. 32460294), and the Youth Project of Yunnan Provincial Basic Research Program (No. 202401AU070080).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The authors have no conflicts of interest to declare that are relevant to the content of this article, neither do they have any relevant financial or non-financial interests to disclose.

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Figure 1. Concept map of different heating methods ((a) is a conceptual diagram of soil cultivation indoors with a constant temperature incubator, (b) is a conceptual diagram of temperature elevations in the field crop-soil system with an infrared lamp, and (c) is a conceptual diagram of transferring the high-altitude plant–soil system to a low altitude).
Figure 1. Concept map of different heating methods ((a) is a conceptual diagram of soil cultivation indoors with a constant temperature incubator, (b) is a conceptual diagram of temperature elevations in the field crop-soil system with an infrared lamp, and (c) is a conceptual diagram of transferring the high-altitude plant–soil system to a low altitude).
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Figure 2. Illustration of different heating methods ((a) is a photo of my soil mineralization experiment using a thermostatic incubator, (b) is a photo of an infrared lamp I constructed for field heating on a rice paddy in Yuanyang County, Yunnan Province, southwestern China, and (c) is a photo of PVC cylinders that I used to transfer soils from rice paddies at other elevations in Yuanyang County to rice paddies here).
Figure 2. Illustration of different heating methods ((a) is a photo of my soil mineralization experiment using a thermostatic incubator, (b) is a photo of an infrared lamp I constructed for field heating on a rice paddy in Yuanyang County, Yunnan Province, southwestern China, and (c) is a photo of PVC cylinders that I used to transfer soils from rice paddies at other elevations in Yuanyang County to rice paddies here).
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Figure 3. Effect of precipitation on SOC.( In the figure, the upward arrow indicates that the indicator is rising, and the upward arrow indicates that the indicator is falling. Black dashed arrows and black arrows represent transitions.)
Figure 3. Effect of precipitation on SOC.( In the figure, the upward arrow indicates that the indicator is rising, and the upward arrow indicates that the indicator is falling. Black dashed arrows and black arrows represent transitions.)
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Figure 4. Effect of temperature elevations on SOC. (In the figure, the upward arrow indicates that the indicator is rising, and the upward arrow indi-cates that the indicator is falling. Red dotted arrows and black arrows represent transitions).
Figure 4. Effect of temperature elevations on SOC. (In the figure, the upward arrow indicates that the indicator is rising, and the upward arrow indi-cates that the indicator is falling. Red dotted arrows and black arrows represent transitions).
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Figure 5. Factors of SOC stability.
Figure 5. Factors of SOC stability.
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Table 1. The results of the SOC response to temperature elevations in different land use.
Table 1. The results of the SOC response to temperature elevations in different land use.
Land UseCharacterization of SOC Response to Temperature ElevationsReferences
Grasslands soilWarmer temperatures enhance soil respiration while increasing plant biomass and carbon content of microbial sources. It made the change in SOC insignificant.[38,39,40,41]
Cropland soilChanges in soil organic carbon in agricultural soils caused by temperature elevations are the result of a combination of factors such as soil texture, precipitation, and land management. [42,43]
Alpine swamp soilTemperature elevations increased the soil extractable organic carbon (EOC), MBC, and SOC content. Root inputs were greater than carbon degradation and release.[12]
Temperate forestElevated temperatures caused a forest soil carbon loss of 710 gCm−2, which was a 31% reduction in carbon stocks.[13]
Subtropical forest soilShort-term temperature elevations increase soil heterotrophic respiration, which reduces soil carbon stocks. However, long-term temperature increases increase forest carbon sequestration capacity.[31,44]
Tropical forest soilElevated temperatures accelerate the decomposition of soil organic matter, resulting in a 55% increase in CO2 emissions from soil heterotrophic respiration.[11,45]
Hilly area soilElevated temperatures reduced carbon sequestration by increasing the decomposition of microbial residual charcoal, exacerbating temperature increases and CO2 emissions. Soil carbon decomposition temperature sensitivity decreases with elevation.[46,47,48]
Peatland soilElevated temperature increases lignin phenols and induces enhanced degradation of more unstable SOC molecules. When the temperature was increased by 9 °C, soluble compounds from plant and microbial sources decreased by 30%, corresponding to a loss of −0.79 ± 0.2 mg g−1 per 1 °C increase in temperature. Temperature elevations by 5 °C significantly stimulated soil organic carbon mineralization, increased nitrogenous compounds, and decreased the activities of invertase and urease.[49,50]
Drylands soilThe temperature sensitivity of dryland soil organic carbon is mainly regulated by soil physicochemical properties (pH and salinity ions). Due to the continuous temperature elevations, the protective effect of minerals cannot stop carbon loss in the arid regions of the world.[51,52]
Wetlands soilFor low C/N (<12) soils, soil CH4 emissions are more sensitive to temperature, while for high C/N (>21) soils, soil CO2 emissions are more sensitive to temperature.[53]
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Wu, Y.; Li, H.; Liang, X.; Jiang, M.; He, S.; He, Y. Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations. Agriculture 2025, 15, 1118. https://doi.org/10.3390/agriculture15111118

AMA Style

Wu Y, Li H, Liang X, Jiang M, He S, He Y. Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations. Agriculture. 2025; 15(11):1118. https://doi.org/10.3390/agriculture15111118

Chicago/Turabian Style

Wu, Yonglin, Haitao Li, Xinran Liang, Ming Jiang, Siteng He, and Yongmei He. 2025. "Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations" Agriculture 15, no. 11: 1118. https://doi.org/10.3390/agriculture15111118

APA Style

Wu, Y., Li, H., Liang, X., Jiang, M., He, S., & He, Y. (2025). Mechanisms Behind the Soil Organic Carbon Response to Temperature Elevations. Agriculture, 15(11), 1118. https://doi.org/10.3390/agriculture15111118

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