《Soil Biology & Biochemistry》A new incubation and measurement approach to estimate the temperature response of soil organic matter decomposition.
Authors: Yuan Liu,Nianpeng He,Li Xu,Jing Tian,Yang Gao,Shuai Zheng,Qing Wang,Xuefa Wen,Xingliang Xu,Kuzyakov Yakov

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.
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《Plant and Soil》Important interaction of chemicals, microbial biomass and dissolved substrates in the diel hysteresis loop of soil heterotrophic respiration
Authors: Qing Wang,Nianpeng He,Yuan Liu,Meiling Li,Li Xu,Xuhui Zhou 

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.     
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《Science of Total Environment》Widespread asymmetric response of soil heterotrophic respiration to warming and cooling
Authors: Liu Y, Wen XF, Zhang YH, Tian J, Gao Y, Ostle NJ, Niu SL, Chen SP, Sun XM, He NP. 

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
《Journal of Geophysical Research: Biogeosciences》Soil microbial respiration rate and temperature sensitivity along a north-south forest transect in eastern China: Patterns and influencing factors
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.
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《Ecology & Evolution》Changes in the temperature sensitivity of SOM decomposition with grassland succession: implications for soil C sequestration
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。
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《Geoderma》Strong pulse effects of precipitation events on soil microbial respiration in temperate forests
作者:Wang Qing,He Nianpeng,Liu Yuan,Li Meiling,Xu li

摘要:降水是干旱半干旱地区土壤生物地球化学过程的关键因素。在本研究中,我们选取了两个温带森林的土壤——一个成熟的天然森林和一个退化的次生森林——半干旱地区。研究了模拟降水(达到55%的土壤含水能力)对土壤微生物呼吸速率(RS)的脉冲效应。我们对以下指标进行了高强度的测量(48小时内每隔5分钟测定1次):土壤呼吸最大值(RS-max),达到最大值的时间(TRS-max)和脉冲效应的持续时间(从开始到结束的½RS-max)。RS对模拟降水的响应速度快、强度大。RS-max在退化次生林中明显高于成熟天然林(7.94 g C g soil-1h-1)。相比之下,在退化次生林中脉冲效应和TRS - max的持续时间明显低于成熟的天然林。此外,在退化次生林和成熟的天然林之间,每克土壤的累计微生物呼吸量(ARS -土壤)并无显著差异,但在退化次生林中,每克土壤有机C (ARS‐soc)的累计微生物呼吸量明显高于成熟的天然林。土壤微生物生物量、土壤养分和垃圾氮含量与脉冲效应和TRS - max的持续时间密切相关。土壤物理结构、pH值和垃圾氮含量与RS-max和ARS‐soc之间存在显著的相关性。我们的研究结果表明,土壤微生物呼吸作用对模拟降水的响应快速、强烈。每克C微生物呼吸率可以被用来精确确定全球气候变化的各种场景下不同土样的降水脉冲以及降雨模式的改变对土壤C含量的影响。
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《Glob Chang Biol》Regional variation in the temperature sensitivity of soil organic matter decomposition in China's forests and grasslands
作者:Liu Yuan,He NianPeng,Zhu JianXing,Xu Li,Yu GuiRui,Niu ShuLi,Sun XiaoMin,Wen XueFa

摘要:如何评价土壤有机质(SOM)分解的温度敏感性(Q10)以及高准确度的反馈区域变化,是决定全球碳(C)周期对气候变化的强度和方向的最大不确定因素之一。在本研究中,我们收集了中国22个森林和30个草地的一系列土壤,以探索Q10的区域变化及其潜在机制。我们进行了一项新颖的试验,定期改变温度(5-30摄氏度)(采用PRI-8800全自动变温控制系统实现),同时持续测量土壤微生物呼吸速率。结果表明,在不同的生态系统中,Q10有显著差异,从1.16到3.19(平均1.63)。Q10的顺序如下:高山草原(2.01)>温带草原(1.81)>热带森林(1.59)>温带森林(1.55)>亚热带森林(1.52)。草原的Q10(1.90)明显高于森林(1.54)。此外,Q10随着海拔的增加而显著增加,并随着经度的增加而减少。环境变量和底物属性一起解释了所有站点中Q10的总变化的52%。总的来说,pH值和土壤电导率主要解释了Q10中的空间变化。在所有生态系统类型中,Q10和底物质量之间的负相关关系在很大程度上支持了C质量温度(CQT)假说,这表明低质量的土壤应该具有更高的温度敏感性。此外,据预测,在全球变暖的情况下,海拔最高的高山草原将对气候变化更加敏感。
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《Soil Biology & Biochemistry》The optimum temperature of soil microbial respiration: Patterns and controls
作者:Liu, Yuan   He, Nianpeng   Wen, Xuefa   Xu, Li   Sun, Xiaomin   Yu, Guirui   Liang, Liyin   Schipper, Louis A.

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