Abstract:【Objective】 Soil organic carbon (SOC) is an essential indicator of soil health. It not only provides a carbon source for plant growth and maintains the physical structure of soil, but also releases carbon into the atmosphere in the form of greenhouse gases, such as carbon dioxide. Therefore, it plays a critical role in the global carbon balance. Currently, the world is experiencing climate change characterized predominantly by warming and increasing frequency and intensity of extreme weather events. However, the impacts of the changing climate, including long-term warming and extreme weather events on SOC are not entirely the same. Distinguishing and quantifying the effects of extremely high temperatures (EH) and global warming (GW) on SOC is the key to formulating adaptive strategies.【Method】 In this study, we focused on paddy soils in Zhangzhou of Fujian Province, a typical subtropical region of China. Based on a 1:50,000 detailed soil database, we employed the biogeochemical process model (DeNitrification-DeComposition, DNDC) to simulate SOC dynamics under four climate scenarios: de-trended climate base state (CTRL), extreme high temperatures (EXP_EH), long-term warming (EXP_GW), and measured temperatures (EXP_obs).【Result】 The results revealed that the total amount of carbon sequestered by paddy fields in Zhangzhou from 1980 to 2016 under the four different climate scenarios (CTRL, EXP_EH, EXP_GW, and EXP_obs) was 1,032.17, 952.15, 1,045.98 and 966.03 Gg, with the corresponding average annual sequestration rates of 93.98, 86.70, 95.24, and 87.96 kg·hm-2, respectively. The long-term warming led to a net increase of 13.81 Gg of SOC in paddy fields across Zhangzhou, while extremely high temperatures resulted in a net decrease of 80.02 Gg. The combined effect of these two factors was -66.14 Gg in SOC, indicating that long-term warming promoted the sequestration of organic carbon in paddy soils, while extremely high temperatures reduced the soil carbon sink capacity, with extremely high temperatures exerting a dominant negative effect. Also, the variations in annual carbon sequestration rates between different climate scenarios indicated that extremely high temperatures throughout the years from 1980 to 2016 had a negative effect on carbon sequestration in the paddy soils of Zhangzhou, but the long-term warming effect on SOC turned from positive to negative around the year of 2000. This may be related to the diminishing effect of warming on plant growth over time. The results of grey relational analysis-structural equation modeling also indicated that the clay content, bulk density, and organic fertilizer application rate were most closely associated with the carbon sequestration rate in rice fields of Zhangzhou, followed by the annual average temperature, precipitation, and pH levels. At the county level, climate change had the greatest impact on the carbon sequestration of Nanjing County. Additionally, the extremely high temperatures and long-term warming caused -26.23% and 7.27% impacts on its carbon sequestration rate, respectively. Among subclasses of rice soils, acid sulfate paddy soils were most affected, with -23.05% and 8.10% changes in carbon sequestration rate caused by warming and extremely high temperatures, respectively. Furthermore, among different terrain and topographical areas, the carbon sequestration rate of hilly and mountainous areas was significantly affected by extremely high temperatures and long-term warming, with -8.84% and 1.98% changes, respectively. 【Conclusion】 In conclusion, while the paddy soils in Zhangzhou still maintain a strong carbon sequestration capacity in the context of climate change, the increasing extreme high-temperature events in the future may potentially contribute to greater carbon losses to some extent.

Abstract:【Objective】Biochar has been shown to improve soil physicochemical properties and enhance crop yields. The results of previous studies on soil temperature were inconsistent, the changes of crop emergence rate under the change of biochar application rate were not analyzed in detail, and the relationship between crop emergence rate and soil physicochemical properties such as soil bulk density, temperature and organic carbon was neglected. Thus, it is important to estimate the most appropriate application rate of biochar for improving soil physicochemical properties and crop yield to provide a basis for field management. 【Method】In this paper, a salinization soil in south Xinjiang was researched and field cotton and sugarbeet growth experiments were carried out in plots under different biochar treatments (0, 10, 50, and 100 t·hm-2) and combined with drip irrigation mode under plastic mulching. The improvement extent and influences of biochar application on soil physicochemical properties and crop germination rates were detailed investigated at the biochar application rates. The relationship between germination rates and soil physicochemical properties was further investigated and compared. 【Result】The results showed that the fluctuations of daily air temperature and solar radiation directly affected the fluctuations of soil temperatures in various depths with biochar applications. The increase of biochar application amounts significantly reduced the soil bulk density at the 0-30 cm depths, in which cotton and sugar beet decreased by 0-0.32 and 0.04-0.25 g·cm-3, respectively. The application of biochar at 100 t·hm-2 significantly increased the soil temperature at the 5 cm depth at different growth stages of cotton and sugar beet, but the application of biochar at 10 and 50 t·hm-2 only significantly increased the soil temperatures of the 5 cm depth at seedling and bolling stages of cotton. During the two experimental years of 2018 and 2019, biochar application have significantly increased the soil organic carbon content of cotton and sugar beet at the seedling and harvesting stages by 0.98-13.2 and 0.66-12.1 g·kg-1 if the differences of planting year and growth periods were not considered, respectively. Also, the increase rate was 1.20-7.43 at the cotton seedling stage and 0.66 to 13.2 g·kg-1 at the harvest stage if the differences of planting year and crops were not considered, respectively, and was proportional to the application rates at the seedling stage. The emergence rate of cotton and sugar beet both increased with the increased soil bulk density, and increased first and then decreased with the increased soil temperature. The optimum temperature range for cotton and sugar beet germination was 22 to 26 ℃. The germination rate increased first and then decreased with the increased soil organic carbon contents, indicating that the excess increase of soil organic carbon content caused by high biochar application rates inhibited crop germination. When the application amount of biochar was 10 t·hm-2, the seedling emergence rates of cotton and sugar beet were greater than 0.7, which was higher than that of the other three biochar application rates. However, when the biochar application rate was greater than 10 t·hm-2, the emergence rates of cotton and sugar beet were lower than that of the treatment without biochar application. 【Conclusion】Therefore, a biochar application amount of 10 t·hm-2 is recommended as the optimal amount for cotton and sugar beet field management considering its comprehensive effects on improving soil properties and crop germination rate.

Abstract:【Objective】 Paddy fields are important anthropogenic sources of atmospheric methane. This study is to investigate the methane production and oxidation potentials and their responses to temperature under different rice-based land use types. 【Method】 Soil samples from four typical land use types in Jurong City, Jiangsu Province, including conventional rice area(CR), rice-crayfish rice area(R-CR), rice-crayfish crayfish area(R-CC) and conventional crayfish area(CC) were collected. Laboratory culture experiments were conducted at 5℃, 15℃, 25℃ and 35℃ for 30 days. 【Result】 The results showed that land use transformation had significant effects on methane production potential and methane oxidation potential. The methane production potential was 1.14 μg·g-1·d-1 in the R-CC area, 0.33 μg·g-1·d-1 in the CC area, 0.25 μg·g-1·d-1 in the R-CR area and 0.17 μg·g-1·d-1 in CR area. Also, the values of methane oxidation potential were 1.38 μg·g-1·d-1 in the CR area, 1.01 μg·g-1·d-1 in the CC area, 1.00 μg·g-1·d-1 in the R-CR area and 0.71 μg·g-1·d-1 R-CC area. The methane production potential increased exponentially with the increase in temperature. The average values of methane production potential at 5℃, 15℃, 25℃ and 35℃ were 0.13, 0.26, 0.55 and 0.95 μg·g-1·d-1, respectively. However, the methane oxidation potential was sensitive only at low temperatures. Specifically, the methane oxidation potential at 15℃, 25℃ and 35℃ were significantly different from the methane oxidation potential at 5℃, while there was no significant difference between the three culture temperatures. The average values of methane oxidation potential at 5℃, 15℃, 25℃ and 35℃ are 0.71, 1.14, 1.14 and 1.11 μg·g-1·d-1, respectively.【Conclusion】 Due to differences in water management, feed and nitrogen fertilizer input, substrate and environmental factors led to differences in the activities of methanogenic bacteria and methane-oxidizing bacteria. Therefore, soils with different land use types presented different characteristics of methane production and oxidation potentials. Generally, the methane production potential was more sensitive to temperature than the methane oxidation potential. The soil methane production potential and oxidation potential were significantly affected by temperature or land use type(P < 0.01), but the interaction between the two factors only had a significant impact on soil methane production potential but not on methane oxidation potential.

Abstract:【Objective】Soil hydrothermal parameters are fundamental physical parameters for studying soil thermal and hydraulic transport. Currently, the heat pulse probe HPP) method can synchronously measure soil hydrothermal parameters. However, but this method is limited to point-scale measurements, while the active heated fiber optic (AHFO) method holds the potential to extend the measurement scale to field-scale kilometers. 【Method】To investigate the errors of AHFO, we conducted comparative experiments between the AHFO and the HPP methods for measuring soil hydrothermal parameters. 【Result】 The results showed that, using the HPP method as a reference, the root mean square error (RMSE) of thermal conductivity measured by the AHFO method was 0.13 W·m–1.·℃–1. The thermal conductivity measured by the AHFO was significantly higher than that by the HPP method. This difference was attributed to the significant increase in temperature during the measurement by fiber optic which led to a temperature effect on the soil thermal conductivity around the fiber optic.【Conclusion】The measurement of error order of soil hydrothermal parameters using the AHFO method mainly originates from the contact thermal resistance between multiple interfaces (fiber optic core-air layer-metal layer-sheath-soil), the temperature sensitivity of the fiber optic, noise interference, and moisture migration under temperature gradients. This study can provide a theoretical reference for improving the accuracy of soil hydrothermal parameter determination by the AHFO method.

Abstract:【Objective】Sheath blight (ShB) is a soil-borne disease, whose occurrence and development seriously threatens rice (Oryza sativa L.) production. However, it is still unclear how elevated CO2 concentration ([CO2]) and temperature affect pathogenesis-related proteins (PR proteins) and defense enzymes in plants infected with Rhizoctonia solani.【Method】In this study, temperature by free-air CO2 enrichment(T-FACE) system was used with four treatments: ambient condition; elevated [CO2]([CO2] up to 590 μmol·mol–1); elevated temperature (temperature increased 2℃); the combination of elevated [CO2] and elevated temperature. Two cultivars(a susceptible variety, Lemont and a resistant variety, YSBR1) were planted to explore the response of PR proteins and defense enzymes activities in leaves and stems for two cultivars by artificial inoculation of R. solani, as well as basic physical and chemical properties of soil.【Result】Results indicated that there was no significant difference in the growth rate of R. solani on soil extract medium, which was made by bulk soil under elevated [CO2] and temperature. After inoculation with R. solani, the development rate of the ShB lesion was not related to the basic physical and chemical properties of soil. The combination of elevated [CO2] and elevated temperature induced different effects on PR proteins and defense enzymes activities in the leaves of two cultivars. For the PR proteins and defense enzymes in stems, the combination of elevated [CO2] and elevated temperature obviously increased the catalase (CAT), phenylalanine ammonia-lyase (PAL), β-1, 3-glucanase (GLU) or superoxide dismutase (SOD) activities for both Lemont and YSBR1. For different cultivars, after being infected with R. solani, the activities of PR proteins and defense enzymes in the leaves and SOD and CAT in the stems for YSBR1 were significantly higher than those for Lemont under different treatments, and the development rate of ShB lesion for YSBR1 was significantly lower than that for Lemont. During the whole disease infection, elevated [CO2] and the combination of elevated [CO2] and elevated temperature both significantly increased the development rate of rice ShB for Lemont by 21%-45%, but not for YSBR1. The correlation analysis showed that under different [CO2] and temperature treatments, the development rate of ShB was significantly positively correlated with GLU activity in stems for Lemont and YSBR1.【Conclusion】After inoculated R.solani, the defense reaction formed by PR proteins and defense enzymes in resistant cultivar can effectively reduce the effect of elevated [CO2] and temperature on the development rate of ShB in the future. This study can provide applications for breeding ShB-resistant cultivars to ensure global rice production under future climate change.

Abstract:Temperature and exogenous arsenic are important factors affecting rice growth. Due to climate warming, rice growth is affected by a combination of temperature and arsenic in rice fields contaminated by arsenic. Clarifying the combination can provide a theoretical basis for rice management and safety production.【Method】Germination and culture experiments were carried out in the artificial climate chamber under the condition of different exogenous arsenic concentrations [0(As0), 0.5(As0.5) and 1(As1) mg`L-1] and different temperature simulations [daytime/nighttime 30℃/25℃(T0) and 35℃/30 ℃(T1)] using eight common rice varieties in Jiangsu Province. Seed germination, seedling growth and arsenic uptake of different rice varieties were analysed. 【Result】The results showed that exogenous arsenic inhibited sprout length and vigor index of rice. Compared with T0As0, T0As1 reduced the sprout length and vigor index of different rice varieties by 13.69%-43.34% and 28.14%-52.88%, respectively, and the effect of temperature on rice seed germination was related to rice varieties. Under the condition of T1 treatment, the germination rate, sprout length and vigor index of Yanliangyou 1618 were better than those of other varieties. The interaction of temperature and exogenous arsenic significantly decreased the sprout length (P < 0.05). Compared with T0As0, T1As1 decreased sprout length by 5.66%-43.34%. Also, single temperature or exogenous arsenic had a significant effect on rice root length and root vigor. Compared with T0As0, T0As1 reduced root vigor by 3.01%-58.21%. The interaction of temperature and exogenous arsenic inhibited rice root length and root vigor. Compared with T0As0, T1As1 significantly reduced root vigor of different rice varieties by 53.80%-89.01%. The seedling height and root vigor of different rice varieties had significant differences (P < 0.05) under the same treatment of temperature or exogenous arsenic, among which the seedling height and root vigor of Yanliangyou 888 were at higher levels. The arsenic concentration in rice stems and leaves increased significantly under exogenous arsenic while the arsenic concentration in rice stems and leaves decreased under the increase in temperature. Furthermore, compared with single arsenic treatment, arsenic concentration in rice stems and leaves decreased under the interaction of temperature and exogenous arsenic. 【Conclusion】From the above results, it can be concluded that temperature and exogenous arsenic affected rice growth and arsenic uptake. However, rice growth conditions and arsenic concentration were significantly different among rice varieties. The germination and growth of Yanliangyou 888 and Yanliangyou 1618 were better than other rice varieties under the condition of temperature and exogenous arsenic.

Abstract:【Objective】The purpose of this study was to explore the optimum preparation conditions of bone biochars, their improvement effects on acid soil, and the influence on Al forms from the perspective of soil solid phase and liquid phase.【Method】The anaerobic pyrolysis of pig, chicken, ox, and sheep bone meals were used as raw materials to produce biochars(bone biochars)as ameliorants and three typical acid soils were used.【Result】The results showed that the bone biochars prepared by high-temperature anaerobic pyrolysis were rich in CaO, CaCO3, and Ca5(PO4)3(OH), contained alkaline substances such as NaO and MgO and characterized by many functional groups including -OH. Nevertheless, the alkali content of bone biochar was greatly affected by the pyrolysis temperature. The alkali content was close to the peak value and remained stable at 800 ℃ for chicken and cow bones, and the same at 900 ℃ for pig and sheep bones. Interestingly, the alkali content of these bone biochars was about 90% of the quicklime, which is the best preparation temperature. Also, the biochars effectively increased the pH of acidic red soils from Anhui, Jiangxi, and Guangdong with an original pH of lower than 6. The alkaline substances in bone biochars mainly existed in the form of H+ buffers and the magnitude of the increase in soil pH was inversely proportional to the initial soil pH. After adding 5 g·kg-1 pig, chicken, sheep, and ox bone biochars to the red soils with pH = 4.40, the Al concentration in soil solution decreased by 33%, 34%, 47%, and 41%, respectively, compared with the control, and the content of organically bound Al in solid phase had no significant change(P > 0.05). Bone biochars increased the cation exchange capacity of acidic soil and reduced the content of soil solution Al and exchange Al by promoting the conversion of active Al to adsorbed hydroxyl Al and more stable Al in the soil solid phase.【Conclusion】Bone biochars are rich in nutrients required for plant growth, has the dual characteristics of inorganic and organic amendments, and are high-quality materials that can replace traditional lime as soil amendments for acidic farmlands.

Abstract:【Objective】Soil fauna play an important role in litter decomposition processes through activities such as burrowing and feeding. Besides the quality of litter, climate parameters have been identified as major factors affecting the role of soil fauna on litter decomposition. However, the contribution of soil fauna in litter decomposition and the role of climatic parameters under different land-use patterns are still not clear.【Method】In this paper, meta-analysis was used to quantify the effect sizes of soil fauna on litter decomposition rates. We established a meta-analysis database by collecting the results of 56 publications both in Chinese and English in China from papers published until May 31, 2021. The effect size of soil fauna on litter decomposition rates among three different land-use patterns (i.e., forest, grassland, and farmland), was further tested by a random-effects model. Correlations were tested between environmental factors -temperature, precipitation, litterbag size, latitude, and experimental duration -and the effect size of soil fauna on litter decomposition rates.【Result】Soil fauna increased litter decomposition rate by an average of 8.10%, reaching a significant level among different land-use patterns. Among the three different land-use patterns, the effect of soil fauna on litter decomposition rates was strongest in the farmland (12.36%). Environmental factors were closely correlated with the effect size of soil fauna on litter decomposition rates.【Conclusion】In the forest, effect size significantly increased with temperature, including the average temperature in January and July, and the mean annual temperature (P < 0.01). In grassland, however, the effect size of soil fauna decreased with temperature (P > 0.05). The effect size significantly increased with mean annual precipitation but significantly decreased with altitude (P < 0.01). Besides, with the increase of litterbag size and experimental duration, the effect size values of soil fauna on litter decomposition significantly increased and decreased, respectively.

Abstract:Soil temperature(especially surface temperature)is a key physical quantity in the interaction between land and atmosphere, and plays a very important role in the earth system. Soil temperature prediction technology has always been the core scientific problem in land surface model, numerical weather prediction and climate prediction. This paper systematically reviews the research progress of soil temperature prediction equation, from the classical heat conduction equation to the heat conduction convection equation that takes into account the physical process of vertical movement of soil moisture, from the single sine wave approximation to the Fourier series approximation of the daily change of surface temperature, from the assumption that the diurnal change of convection parameters is constant to the consideration of its diurnal change, and emphatically summarizes the creation, improvement and solution of the soil heat conduction convection equation. Finally, this paper reviews the application of heat conduction convection equation in the study of surface energy balance, vertical movement of soil moisture, water flux, earthquake and frozen soil heat transfer. At the same time, it is pointed out that the influences of soil water phases and plant roots on the heat conduction-convection equation is warranted for the future research of soil temperature prediction equation.

Abstract:【Objective】 The accumulation rate of soil organic matter directly restricts the improvement of productivity of Pinus massoniana (Masson pine) in the process of vegetation restoration in eroded red soil area. The way to solve this problem has been an inevitable development process of Masson pine in eroded red soil area. Heterotrophic respiration, an important part of soil carbon emission, is a key factor affecting soil organic carbon accumulation. Therefore, it is of great significance to study the effects of Masson pine plantation restoration on heterotrophic respiration and its temperature sensitivity in eroded red soil areas. This will enhance our understanding of the carbon output process and effectively increase soil organic matter accumulation in eroded red soil areas. 【Method】 In this study, Masson pine plantations with different restoration years (Y0, Y14, Y31) were selected as the research objects. The effects of vegetation restoration on soil heterotrophic respiration were studied by separating and measuring different respiration components and combining with soil factors such as soil organic carbon, total nitrogen, soil temperature, water content and litter. The structural equation model of heterotrophic respiration between litter, soil temperature, soil nutrients, soil microorganisms and heterotrophic respiration were established to analyze the correlation between heterotrophic respiration and environmental factors in the process of vegetation restoration, and to explore the main factors affecting heterotrophic respiration. 【Result】 The results showed that the heterotrophic respiration (RH) of the pine forests with different recovery years differed significantly. The RH in site Y31 was significantly higher than that in site Y14 and Y0. The RH in site Y0 was only 0.99 μmol·m–2·s–1, while in sites Y14 and Y31 it was 2.20 and 2.80 μmol·m–2·s–1, respectively. Temperature was the main influencing factor of the seasonal variation of heterotrophic respiration, explaining 40.6%(Y0), 62.2%(Y14) and 66.6%(Y31) of the seasonal variation, respectively. During the restoration process, the temperature sensitivity(Q10)of relative humidity increased significantly, which was 1.58, 1.93 and 1.82, respectively. The relative contributions of RH to total soil respiration in different recovery years are 77.94%(Y0), 70.84%(Y14), and 77.35%(Y31). The structural equation model showed that soil organic carbon (SOC), temperature and soil microbial diversity were the main factors affecting soil RH during the restoration of Masson pine. SOC and soil microbial abundance significantly correlated with RH, and soil temperature varied with vegetation restoration which significantly and negatively correlated with RH. 【Conclusion】 The results of this study indicate that the accumulation of SOC and lack of effective physical protection during Masson pine vegetation restoration increase the decomposition of SOC by microorganisms; On the other hand, the reduction of soil environmental temperature, a continuous increase of bacteria and fungi abundance, and an increase of Proteobacteria, Ascomycota and Acidobacteria in the community further aggravate the microbes to the original strength of soil organic matter decomposition. Consequently, the continuous increase of heterotrophic respiration related carbon emissions limits the improvement of carbon sequestration efficiency of Masson pine forests. Therefore, the strong soil heterotrophic respiration in the eroded and degraded red soil area may be the key factor limiting further improvement of soil organic matter.