Authors:
Mengyang You , Diankun Guo , Hongai Shi , Peng He , Martin Burger , Lu Jun Li
Abstract:
Background and aim
Soil organic carbon (SOC) mineralization which relates to SOC stability and sequestration, predicating the SOC stocks under climate change, is affected by land use and exogenous carbon addition. However, how SOC chemical composition and soil enzymes regulate SOC mineralization of grassland and forest soils receiving exogenous C addition is still not well understood.
Methods
Forest and grassland soils were incubated without or with two levels of 13C-enriched glucose, simulating labile C inputs, at 15 and 25 ℃ for 28 days. The priming effect, temperature sensitivity (Q10), enzyme activities and chemical composition of SOC were determined.
Results
Increasing labile C addition and higher temperature accelerated native SOC mineralization in forest and grassland soil. Changes of enzyme C:N and N:P ratio contributed to the differences in CO2 production in forest and grassland soil. In grassland soil, the relationship between soil-derived CO2 production and relative peak areas of SOC at 1420 cm−1 by Fourier-Transform infrared spectroscopy was significant. The temperature sensitivity of the native SOC mineralization in the forest soil amended with 0.8 g glucose-C kg−1 dry soil application was greater than that with 0.4 g glucose-C kg−1 dry soil application, but in the grassland soil, the Q10 of glucose derived CO2 emission was lower after the higher glucose application.
Conclusion
Soil enzyme nutrient ratios and chemical composition of SOC together play an important role in regulating the mineralization of SOC and the Q10 value of external C addition mineralization in forest and grassland soil.
原文链接Authors:
Xuhui Zhou , Zhiqiang Feng , Yixian Yao , Ruiqiang Liu , Junjiong Shao , Shuxian Jia , Yining Gao , Kui Xue , Hongyang Chen , Yuling Fu , Yanghui He
Abstract:
The combination of biochar and nitrogen (N) addition has been proposed as a potential strategy to sustain crop productivity and mitigate climate change by increasing soil fertility, sequestering carbon (C), and reducing soil greenhouse gas emissions. However, our current knowledge about how biochar and N additions interactively alter mineralization of native soil organic C (SOC), which is referred to priming effects (PEs), is largely limited.To address this uncertainty, C3 biochar (pyrolyzing rice straw at 300, 550, and 800 ◦C) and its combination with N fertilizer (urea) were incubated in a C4-derived soils at 25 ◦C. All these 3 types of biochar with different addition rates caused positive priming of native soil organic matter decomposition (up to +58.4%). The maximum negative priming effects (up to − 25.4%) occurred in soil treated with 1% of N-bound biochar pyrolyzed at 300 ◦C. In addition, a negative correlation was found between the priming intensity and soil inorganic N content across all treatments. The decrease in biochar-induced PEs was related with a shift in microbial community composition and reduction in microbial biomass determined by chloroform-fumigation. Such a reduction, however, was not confirmed by PLFA analysis. These findings advance our understanding on the microbial mechanisms mediating net soil C balance with the adequate biochar use for blending traditional mineral fertilizers.
原文链接
Authors:
Mengyu Liu , Yao Yu , Ying Liu , Sha Xue b, Darrell W.S. Tang , Xiaomei Yang
Abstract:
astic pollution in agricultural soils due to polyethylene plastic film mulch used, biodegradable film is being studied as a promising alternative material for sustainable agriculture. However, the impact of biodegradable and polyethylene microplastics on soil carbon remains unclear. The field experiment was conducted with Poly (butyleneadipate-co-terephthalate) debris (PBAT-D, 0.5–2 cm), low-density polyethylene debris (LDPE-D, 0.5–2 cm) and microplastic (LDPE-Mi, 500–1000 μm) contaminated soil (0% (control), 0.05%, 0.1%, 0.2%, 0.5%, 1% and 2% w:w) planted with soybean, to explore potential impacts on soil respiration (Rs), soil organic carbon (SOC) and carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidizable carbon (EOC), particulate organic carbon (POC), mineral-associated organic carbon (MAOC)), and C-enzymes (β-glucosidase, β-xylosidase, cellobiohydrolase). Results showed that PBAT-D, LDPE-D and LDPE-Mi significantly inhibited Rs compared with the control during the flowering and harvesting stages (p < 0.05). SOC significantly increased in the PBAT-D treatments at both stages, and in the LDPE-Mi treatments at the harvesting stage, but decreased in the LDPE-D treatments at the flowering stage. In the PBAT-D treatments, POC increased but DOC and MAOC decreased at both stages. In the LDPE-D treatments, MBC, DOC and EOC significantly decreased but POC increased at both stages. In the LDPE-Mi treatments, MBC and DOC significantly decreased at the harvesting stage, while EOC and MAOC decreased but POC increased at the flowering stage. For C-enzymes, no significant inhibition was observed at the flowering stage, but they were significantly inhibited in all treatments at the harvesting stage. It is concluded that PBAT-D facilitates soil carbon sequestration, which may potentially alter the soil carbon pool and carbon emissions. The key significance of this study is to explore the overall effects of different forms of plastic pollution on soil carbon dynamics, and to inform future efforts to control plastic pollution in farmlands.
原文链接Authors:
Shenliang Zhao , Hua Chai , Yuan Liu , Xiaochun Wang , Chaolian Jiao , Cheng Liu a , Li Xu d, Jie Li , Nianpeng He
Abstract:
How and what soil fauna influence the soil organic matter (SOM) decomposition rate (Rs) and its temperature sensitivity (Q10) have been largely ignored, although this is a crucial matter, especially under the scenario of global change. In this study, a novel approach was adopted with a continuous changing-temperature incubation (daytime, from 7 °C to 22 °C; nighttime, from 22 °C to 7 °C) with rapid and continuous measurement, to examine the effect of soil macrofauna (specifically, earthworms) on Rs and Q10 with three densities (no addition, low density, and high density). According to the results, the earthworms accelerated Rs. Furthermore, Rs with earthworm addition had a symmetrical pattern during daytime and nighttime cycles, which is contrary to traditional soil incubation, with only soil microbe as asymmetrical. More importantly, earthworm addition increased Q10 markedly, ranging from 48% to 67%. Overall, the findings highlight the pivotal role of earthworms as soil macrofauna that regulating soil carbon release, and their effects should be integrated into process-based ecological models in future.
Authors:
Jinyang Zheng , Kees Jan van Groenigen d, Iain P. Hartley , Ran Xue , Mingming Wang , Shuai Zhang , Ting Sun , Wu Yu, Bin Ma, Yu Luo , Zhou Shi , Zhongkui Luo
Abstract:
Soil organic carbon (SOC) mineralization, driven by soil microbial communities, plays a crucial role in the global carbon cycle. However, the temperature sensitivity of microbial preferences for SOC substrates remains poorly understood, limiting our ability to predict SOC dynamics under climate change. Here we combined bacterial community profiling, laboratory incubations, and a pool-based carbon model to investigate the relationships between bacterial species abundances and two SOC pools with fast and slow decay rates, respectively, at different incubation temperatures. Only about half of identified bacterial species is significantly (P < 0.05) associated with the mineralization of the two pools and their temperature sensitivity (Q10). More importantly, we find that the association of the species with the two pools shifts in terms of both magnitude and direction with incubation temperature. The proportion of species associated with the Q10 of fast pool decreased, while those associated with the Q10 of slow pool increased with warming. Meanwhile, species specifically associated with the fast pool exhibit stronger temperature sensitivity compared to species specifically associated with the slow pool at lower temperatures, and vice versa at higher temperatures. These results suggest that common bacterial species associated with SOC mineralization adjust their substrate preferences in response to temperature variations, potentially impacting SOC composition and dynamics under warming. 原文链接Authors:
Ming Gao,Wei Hu,Meng Li,Mingming Guo,Yongsheng Yang
Abstract:
Land-use change directly impacts soil basal respiration (Br), soil microbial attributes, and soil organic matter (SOM) composition. However, the role of soil microbial attributes and SOM composition in influencing soil Br under land-use changes remains largely undetermined. We examined how interactions between soil physicochemical properties, SOM chemical structure, and microbial attributes regulate soil Br across three land-use types, cropland, forest, and grassland, in the Mollisol and Arenosol of Horqin Sandy Land. The results showed that soil Br, phospholipid fatty acid content, and the relative peak areas of aliphatic and aromatic compounds were significantly lower in cropland than in forest and grassland. Additionally, the Arenosol exhibited poorer soil properties compared to the Mollisol (p < 0.05). Soil Br in the Mollisol (3.60–5.56 mgCO2-C kg−1 h−1) was significantly higher than in the Arenosol (0.86–2.60 mgCO2-C kg−1 h−1, p < 0.05). G+/G− ratios and bacteria were identified as the main predictors of Br in the Mollisol and Arenosol, respectively. The structural equation model revealed that microbial attributes are the primary drivers of Br, influencing it indirectly through changes in SOM composition. Our findings are instrumental in understanding the role of microbial attributes in carbon turnover during land-use changes.
原文链接Authors:
Huiling Wang, Hang Jing , Huizhen Ma , Guoliang Wang
Abstract:
The mechanisms by which belowground plant deposits influence soil organic carbon dynamics under increasing nitrogen (N) deposition remain unclear. In this study, ingrowth cores with different mesh sizes (1 µm, 45 µm and 1 mm) were used to investigate the effects of mycelium and fine root deposits on soil dissolved organic matter (DOM) and CO2 emissions under N addition. Results indicated that mycelium did not significantly alter DOM composition or microbial community, whereas several labile (including amino sugars and carbohydrates) and recalcitrant DOM (including lignin and tannin) were enriched in the fine root and coarse root treatments, respectively. The fungal community shifted towards a K-strategy in the presence of mycelium and roots compared to the control treatment (1 µm). N addition increased the abundance of recalcitrant DOM molecules, particular in fine root treatments. Root deposit inputs increased DOM transformation and the complexity of the DOM-microbe network. The associations between microbes and labile carbon were enhanced in the mycelium and fine root treatments. The relationships between oligotrophic Basidiomycota and recalcitrant carbon were strengthened in the coarse root treatment. CO2 emissions in mycelium treatments were inhibited by N addition, primarily due to a decrease in mycorrhizal colonization. Root deposit inputs and DOM-microbe interactions dominated the CO2 emissions in the forest soil under N addition. Our findings confirm the essential role of fine root deposits, in regulating soil CO2 emissions by influencing DOM characteristics under N deposition.
原文链接Authors:
Zhiyun Zhou, Ni Zhang, Yijun Wang & Kelong Chen
Abstract:
Background and aims
Freeze–thaw cycles (FTC) can affect the rates of soil organic carbon (SOC) mineralization and carbon (C) and nitrogen (N) cycling in soils. However, little is known about whether this effect changes with litter inputs, especially for alpine grassland ecosystems.
Methods
Using soil and Litter from Tibetan Plateau alpine meadows, we conducted a 15-day indoor experiment under two FTC regimes (-15 to 15℃ and -10 to 10℃), constant 10℃, and litter addition.
Results
The results showed that the SOC mineralization rates under the I ± 10 and I ± 10L treatments were significantly lower than those of the control by 7.85% and 6.20%, respectively, while the C mineralization rates under the I ± 15L treatment were significantly higher than that of the control by 20.78%. The temperature sensitivity (Q10) was significantly higher under I ± 10 than under I ± 15. The C mineralization rates under the control + L treatment were 42.76% higher than those of the control and induced a significant priming effect (PE), which was significantly lower in the I ± 10L treatment compared to the control + L. Structural equation modeling suggested that FTC indirectly affected C mineralization via changes in ammonium nitrogen (NH4+-N) and microbial biomass carbon (MBC), whereas litter addition directly altered MBC to promote C release.
Conclusion
Our findings suggest that the I ± 10L treatment can reduce the rates of soil C mineralization and PE in alpine swamp meadows. However, the control + L treatment significantly enhances the availability of organic carbon for microbial decomposition, thereby accelerating C release. Therefore, the impact of the reduction in freeze–thaw events under climate warming must be re-evaluated within broader environmental and ecological contexts.
原文链接Abstract: It remains unclear how soil microbes respond to labile organic carbon (LOC) inputs and how temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is affected by LOC inputs in a short-term. In this study, 13C-labeled glucose was added to a pristine grassland soil at four temperatures (10, 15, 20, and 25 °C), and the immediate utilization of LOC and native SOM by microbes was measured minutely in a short-term. We found that the LOC addition stimulated the native SOM decomposition, and elevated temperature enhanced the intensity of microbial response to LOC addition. The ratio between microbial respiration derived from LOC and native SOM increased with higher temperature, and more LOC for respiration. Additionally, LOC addition increased the Q10 of SOM decomposition, and the Q10 of LOC decomposition is higher than that of native SOM. Overall, these findings emphasize the important role of temperature and LOC inputs in soil C cycles. 原文链接
Abstract：Lake Kivu, East Africa, is well known for its huge reservoir of dissolved methane (CH4) and carbon dioxide (CO2) in the stratified deep waters (below 250 m). The methane concentrations of up to ~ 20 mmol/l are sufficiently high for commercial gas extraction and power production. In view of the projected extraction capacity of up to several hundred MW in the next decades, reliable and accurate gas measurement techniques are required to closely monitor the evolution of gas concentrations. For this purpose, an intercomparison campaign for dissolved gas measurements was planned and conducted in March 2018. The applied measurement techniques included on-site mass spectrometry of continuously pumped sample water, gas chromatography of in-situ filled gas bags, an in-situ membrane inlet laser spectrometer sensor and a prototype sensor for total dissolved gas pressure (TDGP). We present the results of three datasets for CH4, two for CO2 and one for TDGP. The resulting methane profiles show a good agreement within a range of around 5–10% in the deep water. We also observe that TDGP measurements in the deep waters are systematically around 5 to 10% lower than TDGP computed from gas concentrations. Part of this difference may be attributed to the non-trivial conversion of concentration to partial pressure in gas-rich Lake Kivu. When comparing our data to past measurements, we cannot verify the previously suggested increase in methane concentrations since 1974. We therefore conclude that the methane and carbon dioxide concentrations in Lake Kivu are currently close to a steady state. 原文链接
Abstract：Carbon monoxide (CO) monitoring in human breath is the focus of many investigations as CO could possibly be used as a marker of various diseases. Detecting CO in human breath remains a challenge because low concentrations (<ppm) must be selectively detected and short response time resolution is needed to detect the end expiratory values reflecting actual alveolar concentrations. A laser spectroscopy based instrument was developed (ProCeas) that fulfils these requirements. The aim of this study was to validate the use of a ProCeas for human breath analysis in order to measure the changes of endogenous exhaled CO (eCO) induced by different inspired fractions of oxygen (FiO2) ranging between 21% and 100%. This study was performed on healthy volunteers. 30 healthy awaked volunteers (including asymptomatic smokers) breathed spontaneously through a facial mask connected to the respiratory circuit of an anesthesiology station. FiO2 was fixed to 21%, 50% and 100% for periods of 5 minutes. CO concentrations were continuously monitored throughout the experiment with a ProCeas connected to the airway circuit. The respiratory cycles being resolved, eCO concentration is defined by the difference between the value at the end of the exhalation phase and the level during inhalation phase. Inhalation of 100% FiO2 increased eCO levels by a factor of four in every subjects (smokers and non smokers). eCO returned in a few minutes to the initial value when FiO2 was switched back to 21%. This magnification of eCO at 21% and 100% FiO2 is greater than those described in previous publications. We hypothesize that these results can be explained by the healthy status of our subjects (with low basal levels of eCO) and also by the better measurement precision of ProCeas.
Abstract: A reliable and precise estimate of the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is critical to predict feedbacks between the global carbon (C) cycle and climate change. In this study, we first summarize two commonly used approaches for estimating Q10 (Approach A: constant temperature incubation and discontinuous measurements, CDM model; Approach B: varying temperature incubation and discontinuous measurements, VDM model). We then introduced a newly developed approach (Approach C, VCM model) that combines rapidly varying temperature incubations and continuous measurements of SOM decomposition rates (Rs) that may be more realistic and suitable for Q10 estimation, especially for large scale estimation. Then, we conducted a 26-day incubation experiment using three different soils to compare the performance of these three approaches for estimating Q10 using R2 and P-values as indicators. Our results demonstrate that the fitting goodness of the exponential model was consistently higher for Approach C, with higher R2 values, lower confidence intervals, and lower P-values in almost all cases compared with Approaches A and B. Furthermore,results showed that Approaches A and B underestimated the Q10 value by 9.5–13% and 2.9–5.7%, respectively,in three different soils throughout the entire incubation period. Compared with traditional commonly used methods, the newly developed Approach C (VCM model) provides a more accurate and rapid estimation of the temperature response of SOM decomposition and can be used for large-scale estimation of Q10. 原文链接
Abstract: Background and aims Increasing the emission of carbon dioxide by heterotrophic respiration (Rh) might lead to global warming. However, issues remain on how Rh responds to changing temperatures, especially with respect to the hysteresis loop in the relationship between Rh and temperature at the daily scale, along with elucidating the underlying mechanisms.
Method We investigated hysteresis loop by measuring Rh in subtropical forest soil at the daily scale (12 h for warm-up (6–30 °C) and cool-down processes (30–6 °C), respectively) using continuous temperature variation and high resolution of measurements over a 56-day incubation period. The ratios of R20 and Q10 between warm-up and cooldown were calculated as the characteristics of diel hysteresis. We measured chemical (pH, conductivity,oxidation-reduction potential), microbial biomass and dissolved substrate (carbon and nitrogen) parameters to explain variation of diel hysteresis.
Results Rh was strongly dependent on temperature, with a clockwise hysteresis loop of Rh between the warm-up and cool-down daily processes. The average value of R20 [at a reference temperature of 20 °C] during the whole incubation period under the warm-up process was significantly higher (46.05 ± 0.96 μgC g−1 d−1) than that under the cool-down process (14.74 ± 0.03 μgC g−1 d−1). In comparison, the average value of Q10 under the cool-down process (5.27 ± 0.2) was significantly higher than that under the warm-up process (1.66 ± 0.02). Redundancy analysis showed that the interaction effects of soil chemical, microbial biomass, and dissolved substrate parameters explain most variation of diel hysteresis:98% variation in R20 and 93.5% variation in Q10.Compared with the weak effect of chemistry parameters on the diel hysteresis, the sole and interactive effects of microbial biomass and substrate were more important,especially their interaction.
Conclusions Interactions of chemical, microbial biomass,and dissolved substrate parameters dominated the variation in diel hysteresis of Rh with temperature,especially the interaction of microbial biomass and dissolved substrate. Of note, Q10 during the warm-up process might be overestimated when using the highly fitted temperature-dependent function of cool-down period.Furthermore, using a constant value of Q10 (Q10=2) in carbon cycle models might be an important source of uncertainty. 原文链接
Abstract: Soil is the largest organic carbon (C) pool in terrestrial ecosystems. Periodic changes in environmental temperature occur diurnally and seasonally; yet, the response of soil organic matter (SOM) decomposition to varying temperatures remains unclear. In this study, we conducted a modified incubation experiment using soils from 16 forest ecosystems in China with periodically and continuously varying incubation temperature to investigate how heterotrophic respiration (Rh) responds to different temperature patterns (both warming and cooling temperature ranging between 5 and 30°C). Our results showed a pronounced asymmetric response of Rh to temperature warming and cooling among the soils of all forest ecosystems, with Rh increasing more rapidly during the warming phase compared to the cooling phase. This asymmetric response of Rh to warming and cooling temperatures was widespread in all soils. In addition, the amplitude of this asymmetric response differed among different forest ecosystems, with subtropical and warm-temperate forest ecosystems exhibiting greater asymmetric responses. Path analyses showed that soil pH and the microbial community explained most of the variation in this asymmetric response. Furthermore, the widespread asymmetric response of Rh to warming and cooling temperatures suggests that accumulated SOM decomposition might be overestimated on average by 20% for warming alone when compared with admix warming and cooling. These findings provide new insights on the responses of Rh to natural shifts in temperature, emphasizing the need to consider this widespread asymmetric response of Rh to warming and cooling phases to predict C-climate feedback with great accuracy, especially under future non-uniform warming scenarios. 原文链接
Authors: Wang Q, He NP, Yu GR, Gao Y, Wen XF, Wang RF, Koerner SE, Yu Q.
Abstract: Soil organic matter is one of the most important carbon (C) pools in terrestrial ecosystems, and future warming from climate change will likely alter soil C storage via temperature effects on microbial respiration. In this study, we collected forest soils from eight locations along a 3700km north-south transect in eastern China (NSTEC). For 8weeks these soils were incubated under a periodically changing temperature range of 6-30 degrees C while frequently measuring soil microbial respiration rate (Rs; each sample about every 20min). This experimental design allowed us to investigate Rs and the temperature sensitivity of Rs (Q(10)) along the NSTEC. Both Rs at 20 degrees C (R-20) and Q(10) significantly increased (logarithmically) with increasing latitude along the NSTEC suggesting that the sensitivity of soil microbial respiration to changing temperatures is higher in forest soils from locations with lower temperature. Our findings from an incubation experiment provide support for the hypothesis that temperature sensitivity of soil microbial respiration increases with biochemical recalcitrance (C quality-temperature hypothesis) across forest soils on a large spatial scale. Furthermore, microbial properties primarily controlled the observed patterns of R-20, whereas both substrate and microbial properties collectively controlled the observed patterns of Q(10). These findings advance our understanding of the driving factors (microbial versus substrate properties) of R-20 and Q(10) as well as the general relationships between temperature sensitivity of soil microbial respiration and environmental factors.
作者：He Nianpeng, Wang Ruomeng, Gao Yang, Dai Jingzhong, Wen Xuefa, Yu Guirui
摘要：了解土壤有机质(SOM)分解的温度敏感性(Q10)对于预测在变暖场景下的陆地生态系统中的土壤碳(C)封存是很重要的。Q10是否会随着生态系统的演替而变化，以及输入SOM影响Q10的化学计量方法在很大程度上仍不为人所知。我们以内蒙古草原的一个演替系列：从自由放牧到31年围栏封育草场为研究对象，设置6个温度(0、5、10、15、20、25°C)和四种基质:控制(CK)、葡萄糖(GLU)、混合牧草叶片(GRA)和苜蓿叶(MED)。结果表明,基底土壤呼吸(20°C)和微生物生物量C(MBC)随草场演替呈对数降低。Q10从自由放牧草地的1.43下降到31年围栏封育草场的1.22。随着底物的增加，Q10显著增加，而Q10的水平随着N的增加而增加。此外，C矿化的积累受新输入SOM和潜伏期温度的控制。随着草地生态系统的演替，Q10的变化受新输入SOM、MBC、SOM质量的化学计量控制，其综合作用可以部分解释中国内蒙古长期放牧草原的土壤碳封存机制。研究结果强调了底物化学计量对Q10的影响还需要进一步研究。
摘要：土壤微生物呼吸（Rh）的温度响应具有重要意义，Rh的最佳温度是准确模拟气候变暖情况下如何应对温度变化的关键参数。然而，在自然生态系统中，关于温度选择的知识仍然有限，特别是在大范围内，这增加了气候预测的不确定性。在这里，我们收集了25个北半球自热带到冷温带森林的土壤，以量化温度选择的区域变化和这种变异的控制机理。采用一种新的系统（PRI-8800全自动变温控制系统），温度逐渐从5度增加到50度，在高频率下测量Rh的温度。结果表明，温度的选择范围从38.5到46.0 ℃（平均值：42.4 ℃）。值得注意的是，这项研究首次证明了温度的选择远高于模型中所使用的假设值（35 ℃），在不同的气候带中有很大的差异，并且随着从热带到冷温带森林土壤的纬度的增加而增加。在一定程度上，我们的研究结果支持了底物供给假说，并与气候适应假说形成了对比。此外，气候、营养和土壤微生物共同调节温度选择的区域变异，共同解释了温度选择中53%的变异。北部地区较高的温度选择表明，这些地区有更大的潜力从土壤中释放更多的二氧化碳，这可能会给全球变暖带来积极的反馈。总之，基于过程的模型应该包含不同区域的温度具有可选性，以改善在气候变暖情况下陆地生态系统的碳动力学的预测。 原文链接
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