Temperature Sensitivity Of Soil Respiration Research Articles

Conversion of a natural evergreen broadleaved forest into coniferous plantations in a subtropical area: effects on composition of soil microbial communities and soil respiration

In this study, we examined how the conversion of native broadleaved forests into plantations of more productive forest species for timber use affects soil microbial community composition at 0–10-cm depth and soil respiration by comparing two 36-year-old plantation forests of Chinese fir (Cunninghamia lanceolata, CF) and Pinus massoniana (PM) with an adjacent relict natural forest of Castanopsis carlesii (NF, ~200 years old) in Sanming, Fujian, China. The soil microbial community composition was determined by phospholipid fatty acid (PLFA) analysis. The monthly in situ soil respiration rate was measured from October 2010 to September 2012. Results showed that the abundance of Gram-negative bacterial PLFAs, actinomycetal PLFAs, and total PLFAs did not vary significantly with forest conversion. The CF soil was characterized by higher abundance of fungal PLFA and lower abundance of Gram-positive bacterial PLFA compared with NF and PM soils. Redundancy analysis (RDA) indicated that the significant change in the composition of soil microbial community was mainly due to fine root biomass and soil pH. Annual soil respiration rate averaged 161.7 mg C m−2 h−1 in NF, 95.1 mg C m−2 h−1 in CF, and 103.2 mg C m−2 h−1 in PM. The NF showed significantly higher mean annual soil CO2 flux (1421 g C m−2 year−1) than CF (837 g C m−2 year−1) and PM (907 g C m−2 year−1). After forest conversion, the apparent temperature sensitivity of soil respiration (Q 10) increased from 1.75 in NF to 2.04 and 1.98 in CF and PM, respectively. The mean annual soil respiration was significantly correlated with soil organic C (SOC) content and abundances of microbial PLFAs except for abundance of fungal PLFA, but not significantly correlated with fine root biomass (<2 mm in diameter) across the different forest soils. The latter behavior may be due to the higher fine root biomass in the CF than in the NF and PM. Our results suggest that studies incorporating the microbial community composition with soil respiration may enhance our understanding of the mechanisms of soil C dynamics.

Effects of crop types and nitrogen fertilization on temperature sensitivity of soil respiration in the semi-arid Loess Plateau

Temperature sensitivity of soil respiration (Q10) is an important mechanism for the possible feedback between global carbon cycle and climate system. Knowledge of how crop types and nitrogen (N) fertilization affect Q10 is critical for estimating soil respiration and carbon cycling in agro-ecosystem. A two-year field experiment was conducted with cold-resistant (winter wheat; Triticum aestivum L.) and thermophilic (spring maize; Zea mays L.) crops at two N fertilization levels (no fertilization (CK) and 160kgNhm−1) from October 2013 to September 2015 in semi-arid Loess Plateau. Annual mean soil respiration and Q10 in maize were 20% (1.85 vs. 1.54μmolm−2s−1) and 36% (2.49 vs. 1.83) higher than that in wheat. Nitrogen fertilization resulted in a 35% increase in annual mean soil respiration (1.95 vs. 1.44μmolm−2s−1) and a 11% decrease in Q10 (2.05 vs. 2.28) compared with the CK treatment. Soil respiration was positively related to root biomass, whereas no significant relationship was found between root biomass and Q10. Therefore, it can be concluded that soil respiration and temperature sensitivity of soil respiration are significantly influenced by crop types and N fertilization regimes, which should be considered in calculating carbon budget in agro-ecosystem using carbon models.

Influences of recovery from wildfire and thinning on soil respiration of a Mediterranean mixed forest

The ecosystem recovery after wildfire and thinning practices are both key processes that have great potential to influence fluxes and storage of carbon within Mediterranean semiarid ecosystems. In this study, started 7years after a wildfire, soil respiration (SR) patterns measured from 2008 to 2010 were compared between an unmanaged-undisturbed mature forest stand (UB site) and a naturally regenerated post-wildfire stand (B site) in a Mediterranean mixed forest in Spain. The disturbed stand included a control zone (unthinned forest, BUT site) and a thinned zone (BT site).Our results indicated that SR was lower at naturally regenerated after fire sites (BUT and BT) than at unburnt one. Soil under the canopy layer of pine and oak trees exhibited higher SR rates than bare or herbaceous layer soils, regardless of the site. The effect of thinning was only manifest, with a significant increase of SR, during the 1st year after thinning practices. SR showed a clear soil temperature-dependent seasonal pattern, which was strongly modulated by soil water content (SWC), especially in summer. Site-specific polynomial regression models were defined to describe SR responses, being mainly controlled by both soil temperature (Ts) and SWC at UB site, or Ts at burnt sites. The sensitivity of SR rate to Ts variations (Q10) ranged between 0.20 and 6.89, with mean annual values varying between 0.92 and 1.35. Q10 values were higher at BT than at UB-BUT sites. The results revealed a significant, non-linear dependence, of Q10 on both Ts and SWC at UB site, and on Ts at both burnt sites. This study contributes to (i) improve the understanding of how natural recovery and management practices affect soil respiration in a Mediterranean forest during their early stages after fire disturbance and (ii) highlight the importance of Q10 values <1 which emphasizes drought stress effect on SR temperature sensitivity.

An inversion approach for determining distribution of production and temperature sensitivity of soil respiration

Abstract. Physical soil properties create lags between temperature change and corresponding soil responses, which obscure true Q10 (temperature sensitivity) values and other biophysical parameters such as depth of production. This study examines an inversion approach for estimating Q10 and e-folding depth of CO2 production (Zp) using physically based soil models, constrained by observed high-frequency surface fluxes and/or concentrations. Our inversion strategy uses a one-dimensional (1-D) multi-layered soil model that simulates realistic temperature and gas diffusion. We tested inversion scenarios on synthetic data using a range of constraining parameters, time-averaging techniques, mechanisms to improve computational efficiency, and various methods of incorporating real data into the model. Overall, we have found that with carefully constrained data, inversion was possible. While inversions using exclusively surface-flux measurements could succeed, constraining the inversion using multiple shallow subsurface CO2 measurements proved to be most successful. Inversions constrained by these shallow measurements returned Q10 and Zp values with average errors of 1.85 and 0.16 % respectively. This work is a first step toward building a reliable framework for removing physical effects from high-frequency soil CO2 data. Ultimately, we hope that this process will lead to better estimates of biophysical soil parameters and their variability on short timescales.

Diurnal and seasonal variations of soil respiration rate under different row-spacing in a Panicum virgatum L. field on semi-arid Loess Plateau of China

Soil respiration (SR) in crop field is affected by environmental factors, agronomic practices and crop types. To clarify how planting density affects the SR dynamics in switchgrass (Panicum virgatum L.) field on the semi-arid Loess Plateau, this research investigated diurnal and seasonal changes of soil respiration rate (RS) under three different row-spacing treatments (20, 40 and 60 cm) in the fourth growing year of switchgrass. Results showed that RS presented a pronounced seasonality under all row-spacing treatments. The highest daily average RS values appeared in August, while the lowest (P<0.05) were in September for each row-spacing. Diurnal variations of RS exhibited single-peak curves in each month. Daily average RS increased significantly as row-spacing enlarged during May and August but there was no significant difference among row-spacing treatments in September. Soil water storage in the depth of 0–100 cm had no significant difference (P>0.05) among the row-spacing treatments, and similar results were found for soil temperature in 0–15 cm soil depth. Soil respiration temperature sensitivity (Q10) values were 1.0–3.7 during the growing months, which were strongly correlated with air temperature in May and June and the soil temperature at 15 cm depth in August. Higher aboveground biomass production and lower RS in most growth months indicated that 20 cm row-spacing treatment was beneficial for increasing the carbon fixation in switchgrass field. Results also implied that it is necessary to take into account the influence of phenology and root growth of switchgrass on soil respiration for accurately evaluating the carbon cycle in the region.

Soil respiration and its temperature sensitivity in agricultural and afforested poplar plantation systems in northern Alberta

The effect of land use change from agricultural to short rotation woody crops on soil respiration and its temperature sensitivity is not fully understood. We studied the effect of land use change on soil respiration, in a factorial experiment, 4 years after converting an agricultural field to a Walker poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantation in the boreal region of northeastern Alberta. Overall, total soil respiration was greater in the agricultural plots (planted to alfalfa, Medicago sativa L.) than in the poplar plots. Soil respiration and soil temperature at the 10-cm depth in both land uses had similar seasonal and diurnal variations. The season-long temperature sensitivity (Q10) of daily and nighttime soil respiration in the alfalfa plots was greater than that in the poplar plots, with Q10 values of 5.4 vs. 4.9, respectively. Our data also show that, 4 years after land use conversion, the heterotrophic respiration was smaller in the poplar plots than in the adjacent agricultural plots, indicating potential benefits of plantation establishment in reducing heterotrophic respiration. However, the temperature sensitivity of soil respiration based on monthly nighttime rates, which minimizes the plant phenological influences, was greater in the poplar plantation, suggesting that soil respiration could become greater in the poplar plantation under a future warmer climate. We conclude that establishment of poplar plantations, which are known to have a fast rate of biomass production for long-term carbon storage, may help mitigate climate change by reducing heterotrophic and total soil respiration in the Canadian boreal region, but the long-term implications (e.g., changes in the temperature sensitivity of soil respiration over time) need to be further studied.

Low soil moisture during hot periods drives apparent negative temperature sensitivity of soil respiration in a dryland ecosystem: a multi-model comparison

Arid and semiarid ecosystems (drylands) may dominate the trajectory of biosphere-to-atmosphere carbon (C) exchange, and understanding dryland CO2 efflux is important for C cycling at the global-scale. However, unknowns remain regarding how temperature and moisture interact to regulate dryland soil respiration (R s ), while ‘islands of fertility’ in drylands create spatially heterogeneous R s . At a site in southeastern Utah, USA we added or removed litter (0–650 % of control) in plots associated with either shrubs or biological soil crust-dominated interspaces between vascular plants. We measured R s , soil temperature (Ts), and water content (θ) repeatedly from October 2013 to November 2014. R s was highest following rain in late summer at Ts ~30 °C, and lowest mid-summer at Ts > 40 °C, resulting in apparent negative temperature sensitivity of R s at high temperatures, and positive temperature sensitivity at low-moderate temperatures. We used Bayesian statistical methods to compare models capturing a range of hypothesized relationships between Ts, θ, and R s . The best model indicates that apparent negative temperature sensitivity of R s at high Ts reflects the control of water content, not high temperatures. Modeled Q10 ranged from 2.7 to 1.4 between 5 and 45 °C. Litter addition had no effect on Q10 or reference respiration (R ref = R s at 20 °C and optimum θ) beneath shrubs, and little effect on R ref in interspaces, yet R ref was 1.5 times higher beneath shrubs than in interspaces. Altogether, these results suggest reduced R s often observed at high Ts in drylands is dominated by the control of θ, and, on shorter-timescales, variable litter inputs exert minimal control over R s .

Nanodeserts: A Conjecture in Nanotechnology to Enhance Quasi-Photosynthetic CO2Absorption

This paper advances “nanodeserts” as a conjecture on the possibility of developing the hierarchical structured polymeric nanomaterials for enhancing abiotic CO2fixation in the soil-groundwater system beneath deserts (termed as quasi-photosynthetic CO2absorption). Arid and semiarid deserts ecosystems approximately characterize one-third of the Earth’s land surface but play an unsung role in the carbon cycling, considering the huge potentials of such CO2absorption to expand insights to the long-sought missing CO2sink and the naturally unneglectable turbulence in temperature sensitivities of soil respiration it produced. “Nanodeserts” as a reconciled concept not only indicate a conjecture in nanotechnology to enhance quasi-photosynthetic CO2absorption, but also aim to present to the desert researchers a better understanding of the footprints of abiotic CO2transport, conversion, and assignment in the soil-groundwater system beneath deserts. Meanwhile, nanodeserts allow a stable temperature sensitivity of soil respiration in deserts by largely reducing the CO2release above the deserts surface and highlighting the abiotic CO2fixation beneath deserts. This may be no longer a novelty in the future.

城市绿地土壤呼吸速率的变化特征及其影响因子

PDF HTML阅读 XML下载 导出引用 引用提醒 城市绿地土壤呼吸速率的变化特征及其影响因子 DOI: 10.5846/stxb201601080058 作者: 作者单位: 广东工业大学,广东省环境科学研究院,广东省环境科学研究院,福建农林大学,广东省环境科学研究院,广东工业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学青年基金资助项目（31470703） Controlling factors of variation in soil respiration rate in urban green-space ecosystems Author: Affiliation: Guangdong University of Technology,Guangdong Provincial Academy of Environmental Science,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:城市绿地土壤呼吸作用深刻影响着城市生态系统碳循环过程，强化城市绿地土壤呼吸速率（Rs）的变化特征及其影响因素的研究，可揭示绿地在城市生态系统碳循环过程中的作用，为优化布局城市绿地和实现低碳排放目标提供科学依据。以广州市海珠湖公园的疏林、灌丛和草地3种典型植被类型的土壤为研究对象，于2013年11月-2014年10月采用静态箱-气相色谱法对公园绿地Rs进行跟踪观测。结果表明：海珠湖公园城市绿地在干湿季节中Rs差异显著；干季Rs较低且波动幅度较小，疏林、灌丛和草地的Rs变化范围分别为（1.66±0.18）-（3.26±0.20）μmol m-2 s-1、（1.27±0.15）-（3.67±0.16）μmol m-2 s-1和（1.94±0.08）-（6.82±1.13）μmol m-2 s-1；湿季Rs较高且波动幅度较大，疏林、灌丛和草地的Rs变化范围分别为（3.53±0.46）-（13.81±1.31）μmol m-2 s-1、（2.82±0.22）-（12.72±1.16）μmol m-2 s-1和（2.80±0.30）-（9.83±0.96）μmol m-2 s-1。T10和VWC10均对土壤呼吸过程有重要的影响，进一步通过回归分析得出，土壤10cm处温度（T10）和体积含水量（VWC10）分别解释Rs时间变异的40%左右和10-24%左右。T10和VWC10相互影响、共同作用于土壤呼吸过程，双因素复合模型的解释能力较单因素模型明显提高，均在50%以上，复合模型为Rs=α·exp（β·T10+γ·VWC10）。干湿季土壤呼吸的温度敏感性（Q10）有明显差异，湿季的Q10比干季的分别高0.44、0.70和0.46。 Abstract:Soil respiration is a major component of the carbon cycle in terrestrial ecosystems, and small changes have a significant effect on CO2 concentration in the atmosphere. Previous studies from different terrestrial ecosystems have confirmed that soil respiration is related to both global climate change and the carbon cycle. However, many studies have focused on non-urban ecosystems, such as forests, farmlands, and grasslands, while fewer studies have examined soil respiration in urban green-space ecosystems. In particular, few studies have addressed whether soil respiration is affected by different vegetation types in urban green-space ecosystems. This research explored soil respiration rate (Rs) in three different vegetation types in urban green-space, to provide basic scientific data on the contribution of urban green-space to the carbon cycle in urban ecosystems. Results will also facilitate the optimization of landscape patterns in urban green-spaces to reduce carbon emissions. In this study, Rs of three representative vegetation types (woodland, scrubland, and grassland) were investigated in Haizhu Lake Park of Guangzhou, Guangdong Province, China. From November 2013 to October 2014, we measured Rs monthly using a static chamber and gas chromatography, while simultaneously measuring soil temperature and volumetric water content. Results showed a significant difference in Rs between the wet and dry seasons. A relatively lower Rs, with less fluctuation, was noted in the dry season:(1.66±0.18)-(3.26±0.20) μmol m-2 s-1 for woodland, (1.27±0.15)-(3.67±0.16) μmol m-2 s-1 for scrubland, and (1.94±0.08)-(6.82±1.13) μmol m-2 s-1 for grassland. Conversely, a relatively higher Rs, with much more fluctuation, was noted in the wet season:(3.53±0.46)-(13.81±1.31) μmol m-2 s-1 for woodland, (2.82±0.22)-(12.72±1.16) μmol m-2 s-1 for scrubland, and (2.80±0.30)-(9.83±0.96) μmol m-2 s-1 for grassland. In addition, environmental factors that influenced soil respiration were very complicated in these urban green-space ecosystems, and two relatively important factors were soil temperature at 10 cm depth (T10) and soil volumetric water content at 10 cm depth (VWC10). Regression analysis showed that the exponential model explained the relationship between T10 and Rs well; T10 explained approximately 40%, while VWC10 explained 10%-24% of Rs variation across months. Notably, a dual-factor (including both T10 and VWC10) model:Rs=α·exp (βT10+γVWC10), better explained Rs variation across months, accounting for over 50% of Rs variation. Furthermore, a significant difference was noted in temperature sensitivity of soil respiration (expressed as Q10) between the wet and dry seasons; the wet season had a greater Q10 value than did the dry season (0.44, 1.15and 0.46, respectively). This study analyzed the differences in soil respiration and influential factors (T10 and VWC10) between three typical vegetation types in urban green-space ecosystems. However, there are many other potentially influential factors that were not considered, and further researcher is needed to explore these in the future. 参考文献 相似文献 引证文献

人工模拟降水条件下旱作农田土壤“Birch效应”及其响应机制

PDF HTML阅读 XML下载 导出引用 引用提醒 人工模拟降水条件下旱作农田土壤“Birch效应”及其响应机制 DOI: 10.5846/stxb201403120428 作者: 作者单位: 西北大学,西北大学,西北大学,中国科学院水利部水土保持研究所,ARS Northern Plains Agricultural Research Laboratory 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31270484,41171033);教育部科技重点项目(209123);西北大学研究生自主创新项目(YZZ13006) Response of soil "Birch Effect" to simulated rainfalls in dry croplands Author: Affiliation: Northwest university,Northwest university,Northwest university,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:降水事件引起干土复湿刺激土壤CO2脉冲释放的现象被称为"Birch效应",其作用机制可能是降水刺激土壤"底物供给"增加或引起土壤"微生物胁迫"所致。为深入了解土壤"Birch效应"对降水格局改变的响应过程及内在机制,在冬小麦拔节期和夏闲期分别进行了不同降水量(1-32 mm)人工模拟降水实验,系统观测了降水后0-72 h土壤呼吸及土壤碳组分变化特征,结果表明:土壤呼吸随降水量的增大而增强,1-16 mm降水土壤呼吸峰值出现在降水后4 h,而32 mm降水土壤呼吸峰值出现时间滞后了4 h。与较小降水量相比,较大的降水量能增加土壤呼吸但会推迟土壤呼吸峰值出现时间。土壤呼吸速率峰值(SR-P)与降水量(P)呈幂相关(拔节期:SR-P=0.97P0.09, R2=0.5, P < 0.05;夏闲期:SR-P=1.07P0.09, R2=0.98, P < 0.01)。降水后72 h累积CO2释放量(CO2-P)与降水量呈线性相关(拔节期:CO2-P=0.03P+5.99, R2=0.58, P < 0.05;夏闲期:CO2-P=0.11P+6.04, R2=0.86, P < 0.01)。土壤呼吸温度敏感性系数和降水量之间存在二次曲线关系(拔节期:Q10=-0.007P2+0.2P+0.7, R2=0.32P < 0.05;夏闲期:Q10=-0.01P2+0.3P+0.2, R2=0.86, P < 0.01)。逐步回归分析表明,冬小麦拔节期所有降水量处理土壤呼吸与土壤微生物量碳相关性均达到显著水平(P < 0.05),指示土壤"Birch效应"是由"微生物胁迫"所致。而在夏闲期,当降水量小于8 mm时土壤呼吸与微生物量碳相关性显著,即以微生物胁迫机制占主导;8 mm降水处理下土壤呼吸与氯仿熏蒸-K2SO4提取态有机碳相关性达到极显著水平,指示则为两种机制共同起作用,而当降水量大于16 mm时,土壤呼吸主要与可提取态有机碳显著相关,"Birch"效应转为以底物供给机制占主导。与夏闲期相比,冬小麦拔节期作物生长会削弱"Birch效应",并改变其响应机制。 Abstract:In the dry cropping lands, soil rewetting due to precipitation can stimulate soil CO2 efflux pulses, which is called the "Birch Effect". Two types of responding mechanisms:"Substrate supply" and "Microbial stress", were proposed to explain the soil "Birch effect". To elucidate how precipitation change affects the "Birch effect "and its responding mechanism, we conducted precipitation simulation experiments in a winter wheat field to measure the short-term response of precipitation levels(1-32 mm) on soil respiration from 0 to 72 h at the jointing stage and during the summer fallow period on the Loess Plateau. The results showed that soil respiration peaked at 4 h with 1 to 16 mm of precipitation, but the peak was delayed by another 4 h at 32 mm precipitation. Higher precipitation delayed, but increased soil respiration compared to lower precipitation. The peak value for the soil respiration rate(SR-P) increased exponentially with increased precipitation(P)(jointing:SR-P=0.97P0.09, R2=0.5, P < 0.05, fallow:SR-P=1.07P0.09, R2=0.98, P < 0.01). Cumulative soil respiration after 72 h(CO2-P) increased linearly with the precipitation level(jointing:CO2-P=0.03P+5.99, R2=0.58, P < 0.05; fallow:CO2-P=0.11P+6.04, R2=0.86, P < 0.01). The temperature sensitivity of soil respiration(Q10) was correlated binomially with the precipitation level(jointing:Q10=-0.007P2+0.2P+0.7, R2=0.32, P < 0.05; fallow:Q10=-0.01P2+0.3P+0.2, R2=0.86, P < 0.01). Stepwise correlation analysis between soil carbon fractions and soil respiration rate showed that soil respiration rate was significantly correlated with soil microbial biomass C at the jointing stage for all precipitation levels, indicating that a "microbial stress" mechanism dominated the "Birch effect" during growing season. However, during summer fallow period, soil respiration rate was significantly correlated with microbial biomass C, which suggested "microbial stress", when the precipitation amount was lower than 8 mm, but correlated with chloroform-fumigated extracted C, which suggested that both mechanisms were operating when precipitation amount was equal to 8 mm. However, soil respiration was significantly correlated with K2SO4-extracted soil C when precipitation amount was equal to or higher than 16 mm, indicating a shift to the "Substrate supply" mechanism. Compared with that during the summer fallow period, the soil "Birch effect" was weaker and its responding mechanism had changed at the wheat jointing stage due to root respiration and shading effects. 参考文献 相似文献 引证文献

Influence of Staphylococcus aureus RecA-LexA system on photoinactivation efficacy

In order to understand the variations of soil respiration with the controlling environmental factors, continuous monitoring was carried out in Hulunber meadow steppe by an automated chamber system, LI-8150, from 2009 to 2011. The results showed that soil respiration exhibited an apparent diurnal variation and seasonal dynamics. Diel maximum soil respiration often appeared between 13:00 and 14:00, while the minimum occurred between 4:00 and 5:00 in the morning. Soil respiration in the growing season from May to September was higher than that in the non-growing season. The peak value often occurred in July and August and the lowest was close to zero in winter. Soil respiration had a significant exponential relationship with soil temperature at 5 cm depth (P < 0.01), which could explain the 86.1–91.1% variation in soil respiration. A significant linear relationship was indicated between soil respiration and soil water content at 10 cm depth (P < 0.05). Soil respirations in 2009, 2010 and 2011 were estimated to be 465.0 gC m−2, 539.2 gC m−2 and 553.2 gC m−2 respectively. In addition, the temperature sensitivities of soil respiration (Q10) were calculated as 3.32, 3.55 and 4.05, respectively. The value of Q10 could cause a lower evaluation derived from observation in a short time, such as considering only the growing season. Field observation of soil respiration should cover all the possible time in the whole year, including the growing and non-growing seasons.

A simple estimate of the carbon budget for burned and unburned Pinus densiflora forests at Samcheok-si, South Korea

To clarify the effects of forest fire on the carbon budget of a forest ecosystem, this study compared the seasonal variation of soil respiration, net primary production and net ecosystem production (NEP) over the year in unburned and burned Pinus densiflora forest areas. The annual net carbon storage (i.e., NPP) was <TEX>$5.75t\;C\;ha^{-1}$</TEX> in the unburned site and <TEX>$2.14t\;C\;ha^{-1}$</TEX> in the burned site in 2012. The temperature sensitivity of soil respiration (i.e., <TEX>$Q_{10}$</TEX> value) was higher in the unburned site than in the burned site. The annual soil respiration rate was estimated by the exponential regression equation with the soil temperatures continuously measured at the soil depth of 10 cm. The estimated annual soil respiration and heterotrophic respiration (HR) rates were 8.66 and <TEX>$4.50t\;C\;ha^{-1}yr^{-1}$</TEX> in the unburned site and 4.08 and <TEX>$2.12t\;C\;ha^{-1}yr^{-1}$</TEX> in the burned site, respectively. The estimated annual NEP in the unburned and burned forest areas was found to be 1.25 and <TEX>$0.02t\;C\;ha^{-1}yr^{-1}$</TEX>, respectively. Our results indicate that the differences of carbon budget and cycling between both study sites are considerably correlated with the losses of living plant biomass, insufficient nutrients and low organic materials in the forest soil due to severe damages caused by the forest fire. The burned Pinus densiflora forest area requires at least 50 years to attain the natural conditions of the forest ecosystem prior to the forest fire.

Tree-scale spatial variation of soil respiration and its influence factors in apple orchard in Loess Plateau

Although small-scale spatial variation of soil respiration has been studied in a wide variety of ecosystems, there are few studies investigating the spatial variation of soil respiration at tree-scale. An inaccurate estimation of soil respiration would be obtained if the spatial variation of soil respiration was ignored. Soil respiration, soil temperature, soil moisture and fine roots biomass were measured in different directions (0, 120, and 240°) at different distances (0.5 and 2 m radial distance) from the trunk of three representative trees for the period 2011–2013 in a mature apple orchard established on the Loess Plateau in 2000. The mean soil respiration rate at 0.5 m-distance was 21, 35 and 42 % higher, respectively. The cumulative soil respiration at 0.5 m-distance was 20, 31, and 38 % higher; and the temperature sensitivity of soil respiration (Q 10) at 0.5 m-distance was 15, 30 and 12 % higher than that at 2 m-distance in 2011, 2012, and 2013, respectively. There was no significant difference in soil temperature and moisture between 0.5 m- and 2 m-distance, whereas fine root biomass at 0.5 m-distance was 64, 108, and 114 % higher than that at 2 m-distance in 2011–2013, respectively. Fine root biomass had a positive linear relationship with accumulative soil respiration and Q 10. Mean annual cumulative soil respiration was 0.46, 0.45, and 0.57 kg C m−2 year−1 in 2011–2013, respectively. Fine root biomass contributed to the spatial variation of soil respiration in apple orchard, and soil respiration at 2 m-distance could represent the C respired in orchard level.

Driving factors of temporal variation in agricultural soil respiration

Investigations of diurnal and seasonal variations in soil respiration support modeling of regional CO2 budgets and therefore in estimating their potential contribution to greenhouse gases. This study quantifies temporal changes in soil respiration and their driving factors in grassland and arable soils located in Northern Germany. Field measurements at an arable site showed diurnal mean soil respiration rates between 67 and 99 mg CO2 m–2 h–1 with a hysteresis effect following changes in mean soil temperatures. Field soil respiration peaked in April at 5767 mg CO2 m–2 day–1, while values below 300 mg CO2 m–2 day–1 were measured in wintertime. Laboratory incubations were carried out in dark open flow chambers at temperatures from 5°C to 40°C, with 5°C intervals, and soil moisture was controlled at 30%, 50%, and 70% of full water holding capacity. Respiration rates were higher in grassland soils than in arable soils when the incubating temperature exceeded 15°C. The respiration rate difference between them rose with increasing temperature. Monthly median values of incubated soil respiration rates ranged from 0 to 26.12 and 0 to 7.84 µg CO2 g–1 dry weight h–1, respectively, in grassland and arable land. A shortage of available substrate leads to a temporal decline in soil respiration rates, as indicated by a decrease in dissolved organic carbon. Temporal Q10 values decreased from about 4.0 to below 1.5 as temperatures increased in the field. Moreover, the results of our laboratory experiments confirmed that soil temperature is the main controlling factor for the Q10 values. Within the temperature interval between 20°C and 30°C, Q10 values were around 2 while the Q10 values of arable soils were slightly lower compared to that of grassland soils. Thus, laboratory studies may underestimate temperature sensitivity of soil respiration, awareness for transforming laboratory data to field conditions must therefore be taken into account.

Temperature sensitivity of soil respiration in China’s forest ecosystems: Patterns and controls

Soil respiration, one of the most important carbon fluxes in terrestrial ecosystems, is very sensitive to climate change. Understanding the spatial patterns of temperature sensitivity of soil respiration (Q10) and its controlling factors is very important to quantify the climate–carbon cycle feedback at regional scales. In this study, we conducted a synthesis of 74 field measurements on Q10 value across China’s forests. Based on the overall data, the Q10 values ranged from 1.10 to 5.18, with a mean value of 2.51. Moreover, the largest relative frequency of Q10 values was within the range of 2.0–3.0. The Q10 value in China’s forests was significantly and negatively correlated with mean annual temperature and mean annual precipitation. However, the Q10 values increased with latitude and altitude but there was no obvious relationship between Q10 and longitude. There were no significant differences in Q10 among evergreen coniferous forest, coniferous-broadleaved mixed forest, deciduous broadleaved forest and deciduous coniferous forest. However, the Q10 of evergreen broadleaved forest was significantly lower than that of evergreen coniferous forest and deciduous coniferous forest. The findings may advance our understanding on the different environmental controls of Q10 of soil respiration and also improve our ability to predict regional-scale soil carbon flux in a changing world.

Changes in temperature sensitivity of soil respiration in the phases of a three-year crop rotation system

Understanding the temperature sensitivity of soil respiration (Q10) and its controlling factors plays an important role in accurately estimating soil respiration and carbon cycling in agro-ecosystems. This manuscript presents a case study on how the Q10 value for soil respiration changes with soil temperature and moisture in the rotation phases. In a three-year crop rotation system (wheat/wheat/millet/pea) in a semi-arid region of China, the soil respiration rate, temperature and moisture were measured under different crop phases from July 2010 to June 2013. The soil respiration rate was significantly lower in the winter wheat phase (1.63μmolm−2s−1) than the millet phase (2.40μmolm−2s−1) and pea phase (2.21μmolm−2s−1). However, the Q10 value was significantly higher in the wheat phase (2.76) than in the millet phase (1.85) and pea phase (1.47). The relationship between the Q10 values and soil temperature followed an exponential decay function in the rotation system, and the Q10 value was stable (1.8) with no obvious variation when the temperature exceeded 15°C. The Q10 value tended to increase with soil moisture until reaching a threshold of 14.7% soil moisture and then declined. Our results indicate that temperature-respiration empirical models should be parameterized according to crop type in the rotation phases, especially when estimating soil respiration in cold-resistant crops under global warming.

Variation of soil respiration and its environmental factors in Hulunber meadow steppe

In order to understand the variations of soil respiration with the controlling environmental factors, continuous monitoring was carried out in Hulunber meadow steppe by an automated chamber system, LI-8150, from 2009 to 2011. The results showed that soil respiration exhibited an apparent diurnal variation and seasonal dynamics. Diel maximum soil respiration often appeared between 13:00 and 14:00, while the minimum occurred between 4:00 and 5:00 in the morning. Soil respiration in the growing season from May to September was higher than that in the non-growing season. The peak value often occurred in July and August and the lowest was close to zero in winter. Soil respiration had a significant exponential relationship with soil temperature at 5 cm depth (P < 0.01), which could explain the 86.1–91.1% variation in soil respiration. A significant linear relationship was indicated between soil respiration and soil water content at 10 cm depth (P < 0.05). Soil respirations in 2009, 2010 and 2011 were estimated to be 465.0 gC m−2, 539.2 gC m−2 and 553.2 gC m−2 respectively. In addition, the temperature sensitivities of soil respiration (Q10) were calculated as 3.32, 3.55 and 4.05, respectively. The value of Q10 could cause a lower evaluation derived from observation in a short time, such as considering only the growing season. Field observation of soil respiration should cover all the possible time in the whole year, including the growing and non-growing seasons.

Effects of different levels of nitrogen fertilization on soil respiration during growing season in winter wheat (Triticum aestivum)

Aims Our objective was to explore the effects of different levels of nitrogen (N) fertilization on soil respiration and its temperature sensitivity during growing season in winter wheat (Triticum aestivum) in East China. Methods Three levels of N fertilization, N1 (15 g·m·a), N2 (30 g·m·a), and N3 (45 g·m·a), and the control group (CK) were set up in winter wheat fields. The LI-8100 Automated Soil CO2 Flux System was used to measure soil respiration rate during the growing season (December 2013 to May 2014) of winter wheat. Important findings During the growing season of winter wheat, mean soil respiration rates of N1, N2 and N3 treatments were 5.29, 6.17 and 6.75 μmol·m·s, respectively, which were 7.8%, 23.6% and 37.8% greater than that of the CK (4.90 μmol·m·s). Compared to CK, the N1, N2, and N3 treatments increased the aboveground biomass by 39.9%, 104.4%, and 200.2%, respectively, and the increases were significantly correlated with total soil respiration during the growing season. Soil respiration increased exponentially with soil temperature at the depth of 5 cm, which explained 65%–75% of the variation (p < 0.05). The temperature sensitivity of soil respiration (Q10) calculated based an exponential equation was between 2.09 and 2.32. These results suggested that nitrogen fertilization promoted plant growth, significantly increased biomass of winter wheat, and stimulated the soil respiration.

Influence of temperature and organic matter content on soil respiration in a deciduous oak forest

The increasing temperature enhances soil respiration differently depend on different conditions (soil moisture, soil organic matter, the activity of soil microbes). It is an essential factor to predicting the effect of climate change on soil respiration. In a temperate deciduous forest (North-Hungary) we added or removal aboveground and belowground litter to determine total soil respiration. We investigated the relationship between total soil CO 2 efflux, soil moisture and soil temperature. Soil CO 2 efflux was measured at each plot using chamber based soil respiration measurements. We determined the temperature sensitivity of soil respiration. The effect of doubled litter was less than the effect of removal. We found that temperature was more influential in the control of soil respiration than soil moisture in litter removal treatments, particularly in the wetter root exclusion treatments (NR and NI) (R 2 : 0.49-0.61). Soil moisture (R 2 : 0.18-0.24) and temperature (R 2 : 0.18-0.20) influenced soil respiration similarly in treatments, where soil was drier (Control, Double Litter, Double Wood). A significantly greater increase in temperature induced higher soil respiration were significantly higher (2-2.5-fold) in root exclusion treatments, where soil was wetter throughout the year, than in control and litter addition treatments. The highest bacterial and fungal count was at the DL treatment but the differences is not significant compared to the Control. The bacterial number at the No Litter, No Root, No Input treatment was significantly lower at the Control. Similar phenomenon can be observed at the fungal too, but the differences are not significant. The results of soil respiration suggest that the soil aridity can reduce soil respiration increases with the temperature increase. Soil bacterial and fungal count results show the higher organic matter content and soil surface cover litter favors the activity.

Temperature sensitivity of soil respiration rates enhanced by microbial community response.

Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.