Temperature Coefficient Of Sensitivity Research Articles

Highly sensitive plasmonics temperature sensor based on photonic crystal fiber with a liquid core

An ultra-high sensitivity temperature sensor based on photonic crystal fiber (PCF) is proposed and demonstrated. The central hole and the two holes coated with nanoscale gold film are assumed to be filled with temperature sensitive liquid. The refractive index of the liquid decreases as the temperature increases with the temperature sensitive coefficient of -3.9 × 10−4/oC. The liquid of the central hole with high refractive index supports liquid-core mode. As the phase matching condition is satisfied, the liquid-core mode couples to the surface plasmon polariton mode and presents energy loss. The influences of the PCF structural parameters and the thickness of the gold film on the resonance wavelength, loss value and sensitivity are studied. The resonance wavelength and confinement loss increase as the temperature increases. The average sensitivity can reach to 9.89 nm/oC (∼25359 nm/RIU) as the temperature changes from 35 °C to 45 °C and the R-square is 0.99992. By replacing the liquid core by silica core, we find the sensitivity is very low. We also compare the PCF without liquid in the holes coated with gold film by our structure and find that the sensitivity is nearly unchanged and the confinement loss is slightly decreased.

Packaging experiments of arrayed waveguide grating

The optical characteristics, spectral responses, crosstalk, and temperature characteristics of alignment and coupling between arrayed waveguide grating chip and single mode fibers with different optical channel cross section dimensions are analyzed and discussed in this paper. The results show that the insertion loss of the AWG device increases with the decrease of the optical channel cross section of arrayed waveguide grating chip, and the position error increases with the alignment and coupling between the arrayed waveguide grating chip and the single mode fibers, and the optical tolerance reduces. The spectrum and crosstalk of device are related to its manufacturing process, and the packaging process has little impact on it. The optical wavelength of AWG optical channel increased with the temperature increasing, and the temperature sensitivity coefficient is about 11.27 pm / °C.

Effects of Simulated Precipitation Reduction on Soil Respiration in a Soybean-Winter Wheat Rotation Cropland

To investigate the effects of precipitation reduction on soil respiration in rainfed croplands, a field experiment was performed in a soybean-winter wheat cropland. A randomized block design including three treatments, viz. control (CK), 20% precipitation reduction (P20%), and 40% precipitation reduction (P40%), was used. Seasonal variabilities in soil respiration, soil temperature, and soil moisture were measured. Rates of soil CO2 production, nitrification and denitrification, and harvested crop biomass were also measured. Results indicated that the seasonal mean soil respiration rates for CK, P20%, and P40% treatments in the soybean growing season were (4.91±0.67), (4.19±0.39), and (4.35±0.32) μmol·(m2·s)-1, respectively. There was no significant difference (P>0.05) in the mean soil respiration rates between treatments during the soybean growing season. The seasonal mean soil respiration rates for CK, P20%, and P40% treatments during the winter wheat growing season were (2.39±0.17), (2.03±0.02), and (1.94±0.05) μmol·(m2·s)-1, respectively. There was a significant (P<0.05) difference in the mean soil respiration rates between treatments during the winter wheat growing season. Precipitation reduction decreased the soil CO2 production rates, but had no obvious impacts on soil nitrification and denitrification rates. Precipitation reduction had no significant (P>0.05) effects on the root, shoot, and seed biomass of soybean, but significantly (P<0.05) decreased the root, shoot, and seed biomass of winter wheat. Soil temperature was the main driver of the seasonal variation in soil respiration. Soil respiration increased exponentially with the increase in soil temperature. There was no significant (P>0.05) difference in the coefficient of temperature sensitivity (Q10) between different treatments. Based on the precipitation reduction experiments of duration longer than one year in previous studies and in our present study, a significant linear regression relationship between the amount of reduced soil respiration and the amount of precipitation reduction was found, indicating that substantial precipitation reduction showed more obvious inhibition effects on soil respiration. This study also suggested that the effects of precipitation reduction on soil respiration varied between crop growing seasons, which may be attributed to the different precipitation intensities in different growing seasons.

Temperature response of ammonia and greenhouse gas emission from manure amended silty clay soil

ABSTRACTSoil temperature plays an important role in organic matter decomposition, thus likely to affect ammonia and gaseous emission from land application of manure. An incubation experiment was conducted to quantify ammonia and greenhouse gas (GHG) (N2O, CO2 and CH4) emissions from manure and urea applied at 215 kg N ha−1 to Fargo-Ryan silty clay soil. Soil (250 g) amended with solid beef manure (SM), straw-bedded solid beef manure (BM), urea only (UO), and control (CT) were incubated at 5, 10, 15, and 25 °C for 31 days at constant 60% water holding capacity (WHC). The cumulative GHGs and NH3 emission generally increased with temperature and highest emission observed at 25 °C. Across temperature levels, 0.11–1.3% and 0.1–0.7% of the total N was lost as N2O and NH3, respectively. Cumulative CO2 emission from manure was higher than UO and CT at all temperatures (P < 0.05). Methane accounted for <0.1% of the total C (CO2 + CH4) emission across temperatures. The Q10 values (temperature sensitivity coefficient) derived from Arrhenius and exponential models ranged 1.5–3.7 for N2O, 1.4–6.4 for CO2, 1.6–5.8 for CH4, and 1.4–5.0 for NH3. Our results demonstrated that temperature significantly influences NH3 and GHG emissions irrespective of soil amendment but the magnitude of emission varied with soil nutrient availability and substrate quality. Overall, the highest temperature resulted in the highest emission of NH3 and GHGs.

A three-year experiment of annual methane and nitrous oxide emissions from the subtropical permanently flooded rice paddy fields of China: Emission factor, temperature sensitivity and fertilizer nitrogen effect

Annual CH4 and N2O emissions from these rice production systems that accounts for over 10% of national rice cultivation of China are rarely reported. To improve understanding of greenhouse gas emissions from croplands in China, we measured methane (CH4) and nitrous oxide (N2O) emissions from the subtropical permanently flooded rice paddy fields through a 3-year field experiment that utilized three nitrogen fertilizer application rates (0 [N0], 150 [N150] and 250 [N250] kg N ha−1) in southwestern China. Results showed that seasonal patterns of CH4 and N2O emissions were consistent with temporal weather patterns. The average annual cumulative CH4 fluxes were in the range of 794 to 883 kg CH4-C ha−1 yr−1 and N2O fluxes ranged from 1.61 to 3.10 kg N2O-N ha−1 yr−1 across the experimental treatments. The Q10 values (soil temperature sensitivity coefficient) of CH4 and N2O emissions were 2.72–3.67 and 3.32–6.05, respectively, for the three treatments. Inconsistent with our hypothesis, the nitrogen fertilizer application did not increase seasonal and annual N2O emissions over three years, compared to the control. Thus, the annual direct N2O emission factors (EFd) averaged 0.07%, which was substantially lower than the IPCC default value of 0.30% for rice paddy fields. Nitrogen fertilizer application significantly decreased the mean seasonal global warming potential (GWP) and yield-scaled GWP for the rice season, whereas this was not true on an annual basis if fallow season was also considered. Since CH4 emission was the major contributor to total GWP, it is necessary to propose mitigation options, which could include draining the floodwater layer and introducing upland crops during the fallow season. However, it will be challenging to reduce N2O emissions and retain soil organic carbon if the floodwater layer is drained and upland crops are introduced during the fallow season.

Dynamics of evaporating drop on heated surfaces with different wettabilities

The dynamics of evaporating sessile drop on a uniformly heated, horizontal, solid substrate is considered. On the basis of lubrication theory and Navier slip condition, an evolution equation for the height of the two-dimensional drop is established. The numerical results show that the drop evolution is governed by capillary force, gravity, thermal capillary force and evaporation. Gravity exerts a promoting effect on drop spreading, while capillary force and thermal capillary force inhibit drop spreading. The typical dynamic features including contact line pinning or partial pinning modes during the drop evaporation are illustrated by changing the temperature-sensitive coefficient in the present model, and the drop lifetime of contact pinning mode is found to be shorter than that of contact line partial pinning mode. Under the same temperature-sensitive coefficient of three interfaces, the drop evolution is indicated with three typical stages: 1) spreading stage, 2) contact line pinning stage, and 3) both contact line and contact angle decreasing stage. As interface tension of liquid-gas or liquid-solid is more sensitive to temperature, the drop evolution is divided into two typical stages: 1) spreading stage and 2) contact line pinning stage. The equilibrium contact angle tends to be smaller and the substrate wettability is improved, leading to the increased spreading speed, the prolonged time of the contact line to reach pinning: the faster the evaporation rate, the shorter the lifetime of drop is. Additionally, the same effect of sensitivity of liquid-gas and liquid-solid interface tension to temperature on the wettability of substrate is observed. When the interface tension of solid-gas is more sensitive to temperature, the drop evolution is characterized in four typical stages: 1) spreading stage, 2) contact line pinning stage, 3) contact line de-pinning and constant contact angle stage, and 4) both contact line and contact angle decreasing stage. The equilibrium contact angle tends to be greater and the substrate wettability is deteriorated, leading the spreading speed to decrease. Hence, it is more effective to manipulate the drop movement in the presence of evaporation by regulating the temperature-sensitive coefficient of the solid-gas interface.

Thermocapillary migration characteristics of self-rewetting drop

The thermocapillary migration characteristics of a self-wetting drop on the non-uniformly heated, horizontal, solid substrate are investigagted by numerical simulation. Based on the lubrication theory, an evolution equation for the height of the two-dimensional drop is established. The substrate underlying the drop is subjected to a temperature gradient which induces surface tension gradient-driven drop deformation and migration. The self-rewetting fluid has non-monotonic dependence of the surface tension on temperature with a well-defined minimum, and the position of the minimum corresponding to the temperature on the substrate is called the critical point. The effect of the relationship between the critical point and the drop position on drop dynamics is analyzed. With the temperature sensitivity coefficient of three interfaces under the same condition, the substrate is illustrated with constant wettability. The direction of drop migration will alter as the initial drop location moves to the left relative to the critical point position, resulting from the variation of the interplay among thermocapillary, gravity, and capillarity forces within the drop. But the drop always migrates toward the high interfacial tension region due to the thermocapillary force. In the presence of substrate wettability variations, the drop migrates toward the low temperature region no matter where the drop is placed relative to the critical point. This is due to the fact that the deterioration of substrate wettability on the right side of the drop prevents the drop from migrating toward the hot region. Under the critical point being on the left or within the drop, as the initial drop location moves to the left relative to the critical point position, the enhancement of the thermocapillary force toward the left leads to increased moving speed of the left contact line and increased spreading area. When the critical point is positioned on the outer right side of the drop, the speed of the left contact line sharply decreases at t=6103, caused by the suddenly deteriorating substrate wettability. Hence, it is effective to manipulate the self-wetting drop movement by regulating the relationship between the critical point and the initial drop location. To inhibit the migration of the drop toward the cold region, the drop should be placed on the right side of the critical point.

Regenerated fiber Bragg grating for fiber laser sensing at high temperatures

Thermally regenerated low-reflectivity fiber Bragg gratings (RFBGs), as one mirror of a resonant cavity, have been introduced as linear-cavity fiber lasers combining with fiber saturable absorbers. The output of lasing presents an optical signal-to-noise ratio of 50 dB and temperature sensitivity coefficient of 15.36 pm/°C for the heating process and 15.46 pm/°C for the cooling process. The lasing wavelength variation and power fluctuation at 700°C are less than 0.02 nm and 0.21 dB, respectively. The RFBG-based fiber laser sensing has displayed good linearity for both the temperature rising and cooling processes, and favorable stability at high temperatures.

Local Temperature Sensitivity Coefficients of a Deterred Spherical Single Base Gun Propellant

Local Temperature Sensitivity Coefficients of a Deterred Spherical Single Base Gun Propellant

Vapor-Assisted Solution Approach for High-Quality Perovskite CH3NH3PbBr3 Thin Films for High-Performance Green Light-Emitting Diode Applications.

The vapor-assisted solution method was developed to prepare high-quality organic-inorganic halide perovskite CH3NH3PbBr3 (MAPbBr3) thin films. We detailedly investigated the effect of evaporation time and temperature of MABr powder on the microstructure, crystallinity, and optical characterizations of MAPbBr3 thin films, and a controllable morphology evolution with varying surface coverage was observed. Temperature-dependent and time-resolved photoluminescence measurements were carried out to investigate the optical transition mechanisms and carrier recombination dynamics of MAPbBr3 thin films. Our results revealed that no structural phase transition occurred within the heating process (10-300 K). In addition to the exciton-related emission, a trapped charge-carrier emission appeared at a critical temperature of 140 K. The corresponding temperature sensitivity coefficient of band gap, exciton binding energy, and optical phonon energy of the MAPbBr3 thin films were extracted from the experimental data. Furthermore, planar perovskite light-emitting diodes (PeLEDs) based on a Al/LiF/TPBi/MAPbBr3/NiO/ITO structure were fabricated, and a high-purity green emission at ∼532 nm with a low line width (25 nm) was achieved. The devices demonstrated remarkable performances with high luminance (6530 cd/m2), current efficiency (8.16 cd/A), external quantum efficiency (4.36%), and power efficiency (4.49 lm/W). This research will provide valuable information for the preparation of high-quality perovskite thin films, facilitating their future applications in novel high-performance PeLEDs.

Characteristics research of pressure sensor based on nanopolysilicon thin films resistors

To further improve the sensitivity temperature characteristics of pressure sensor, a kind of pressure sensor taking nanopolysilicon thin films as piezoresistors is proposed in this paper. On the basis of the microstructure analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) tests, the preparing process of nanopolysilicon thin films is optimized. The effects of film thickness and annealing temperature on the micro-structure of nanopolysilicon thin films were studied, respectively. In order to realize the measurement of external pressure, four nanopolysilicon thin films resistors were arranged at the edges of square silicon diaphragm connected to a Wheatstone bridge, and the chip of the sensor was designed and fabricated on a [Formula: see text] orientation silicon wafer by microelectromechanical system (MEMS) technology. Experimental result shows that when [Formula: see text] = 6.80 mA, the sensitivity of the sensor PS-1 is 0.308 mV/kPa, and the temperature coefficient of sensitivity (TCS) is about −1742 ppm/[Formula: see text]C in the range of −40–140[Formula: see text]C. It is possible to obviously improve the sensitivity temperature characteristics of pressure sensor by the proposed sensors.

Response of Soil Respiration and Heterotrophic Respiration to Returning of Straw and Biochar in Rape-Maize Rotation Systems

Soil respiration has become the main way of farmland ecosystem carbon emissions. Soil respiration and its responses to soil moisture and soil temperature under straw and biochar returning were investigated. Combined soil CO2 fluxes system(ACE-002/OPZ/SC) with the method of root exclusion, this study conducted a long-term field experiment in the national monitor station of soil fertility and fertilizer efficiency of purple soils. The total soil respiration and heterotrophic respiration rate and the soil hydrothermal factors were measured during the growth period of rape and maize in rape-maize rotation systems, and the difference between total soil respiration and heterotrophic respiration was calculated as the contribution of root respiration to soil respiration. There were five treatments including CK(no organic material), CS(straw), CSD(straw+microorganism), BC(biochar), CSBC(50%straw+50%biochar), which were replicated three times. The results showed that straw and biochar returning significantly affected the seasonal variations and the peak of soil respiration. In addition to BC treatment, other treatments promoted soil respiration and cumulative emissions of soil CO2. Soil respiration rate was significantly different under different treatments, the changes in soil respiration rates showed a single peak curve under all treatments, the seasonal variations in soil respiration rates under rape was 0.12-2.29 μmol·(m2·s)-1, displaying an order of CS > CSD > CSBC > CK > BC. Soil respiration was pretty complex in maize season, the seasonal variation in soil respiration rates under rape was 1.02-15.32 μmol·(m2·s)-1, displaying an order of CSD > CS > CSBC > CK > BC, the changes in soil respiration rate presented a double peak curve under CS and CSD and CSBC treatments and a single peak curve under BC and CK treatments. Heterotrophic respiration could explain 86.50%-93.94% of seasonal variations in the soil total respiration, and the contribution of root respiration(26.49%-32.86%) was significantly lower than CK treatment(53.65%).Straw and biochar returning did not change soil temperature and soil moisture. Soil temperature at 5 cm depth had significant effects on the change dynamics of soil respiration rates, but soil moisture did not. Soil temperature at 5 cm depth could explain 82%-94% of the variations in soil respiration. The values of temperature sensitivity coefficient changed from 3.28 to 4.47. Compared with CK treatment, Q10 of CS, CSD and CSBC decreased by 26.62%, 18.12%, 20.58%, respectively, while BC increased by 12.53%. There was no synergistic effect between soil temperature and soil moisture on soil respiration, the dynamic changes of soil respiration rate could be simulated by single factor index function of soil temperature. Overall, soil respiration was significantly promoted by returning of straw, straw+microorganism, straw+biochar, while it was inhibited by returning of biochar.

Temporal dynamics and vertical variations in stem CO2 efflux of Styphnolobium japonicum.

CO2 efflux (ECO2) from stems and branches is highly variable within trees. To investigate the mechanisms underlying the temporal dynamics and vertical variations in ECO2, we measured the stem ECO2 by infrared gas analysis (IRGA) and meteorological conditions at 10 different heights from 0.1 to 3.7m aboveground on two consecutive days every month for 1year in six Styphnolobium japonicum trees with a similar size. The results indicated that the seasonal change in ECO2 roughly followed the seasonal variations in woody tissue temperature (TW) and stem radial diameter increment (Di). Together, TW and Di explained the monthly change in ECO2, and the contributions of TW and Di changed with the stem positions and growth stages. The diurnal patterns of ECO2 differed greatly between the growing and dormant season, showing a bimodal distribution with an obvious midday depression in the former and a unimodal distribution in the latter. The strong vertical variation in the day-time ECO2 of the growing season was mainly caused by the vertical gradients of TW, Di and difference in sapwood volume per unit of the stem surface along the trunk. The temperature-sensitivity coefficient (Q10) was not constant, as assumed in some models, but was instead vertically altered and highly dependent on the measurement temperature. For all stem positions, the highest Q10 value appeared at approximately 5 °C, and both higher and lower temperatures decreased Q10. Our study demonstrated that application of a constant Q10 would cause an estimation error when scaling up chamber-based measurements to annual carbon budgets at the whole-stem level.

Long-term monitoring of ground anchor tensile forces by FBG sensors embedded tendon

Recently, there has been significant interest in structural health monitoring for civil engineering applications. In this research, a specially designed tendon, proposed by embedding FBG sensors into the center king cable of a 7-wire strand tendon, was applied for long-term health monitoring of tensile forces on a ground anchor. To make temperature independent sensors, the effective temperature compensation of FBG sensors must be considered. The temperature sensitivity coefficient

Numerical analysis of highly birefringent photonic crystal fiber for temperature sensing application

In the present paper, we propose and investigate theoretically by full vector finite element method a novel temperature sensor, based on highly birefringent photonic crystal fiber infiltrated with ethanol along the fiber length. Simulation results show a linear dependence of the fiber birefringence with temperature. Birefringence is an increasing function of temperature, and the temperature sensitivity coefficient can reach 7,51×10−6 by Celsius degree. In comparison with other temperature sensors based on birefringent photonic crystal fibers, our designed sensor presents a higher sensitivity.

Effect of Elevated UV-B Radiation on Microbial Biomass C and Soil Respiration in Different Barley Cultivars Under Field Conditions

Elevated ultraviolet-B (UV-B) radiation effect on soil carbon (C) cycling has been regarded as one of the important issues in global change. Field simulating experiment was conducted to investigate the effects of elevated UV-B radiation on the content of microbial biomass C in rhizosphere and non-rhizosphere soils as well as soil respiration in three barley cultivars. The UV-B radiation was set at two levels, i.e., reference (A, ambient UV-B radiation), and elevated by 20% (E, elevated UV-B radiation, 14.4 kJ m−2 day−1). Three barley cultivars were tested including Dan 2, Supi 3, and Supi 4, respectively. The results indicated that elevated UV-B radiation obviously decreased the content of microbial biomass C in rhizosphere and non-rhizosphere soil, but had no effect on the tendency of microbial biomass C in rhizosphere and non-rhizosphere soil during the entire barley growing season. Compared with control (ambient UV-B radiation), elevated UV-B radiation depressed soil respiration rate and its temperature sensitivity coefficients (Q10), especially in barley cultivar Dan 2 and cultivar Supi 3. It is suggested that the different responses of three barley cultivars to elevated UV-B radiation were related to the changes of microbial biomass C and soil respiration.

Seasonal and Inter-Annual Variations in Carbon Dioxide Exchange over an Alpine Grassland in the Eastern Qinghai-Tibetan Plateau.

This work analyzed carbon dioxide exchange and its controlling factors over an alpine grassland on the eastern Qinghai-Tibetan Plateau. The main results show that air temperature and photosynthetically active radiation are two dominant factors controlling daily gross primary production. Soil temperature and soil water content are the main factors controlling ecosystem respiration. Canopy photosynthetic activity is also responsible for the variation of daily ecosystem respiration other than environmental factors. No clear correlation between net ecosystem exchange and environmental factors was observed at daily scale. Temperature sensitive coefficient was observed to increase with larger soil water content. High values of temperature sensitive coefficient occurred during the periods when soil water content was high and grass was active. Annual integrated net ecosystem exchange, gross primary production and ecosystem respiration were -191, 1145 and 954 g C m-2 for 2010, and -250, 975 and 725 g C m-2 for 2011, respectively. Thus, this alpine grassland was a moderate carbon sink in both of the two years. Compared to alpine grasslands on the Qinghai-Tibetan Plateau, this alpine grassland demonstrated a much greater potential for carbon sequestration than others. Annual precipitation is a dominant factor controlling the variation of annual net ecosystem exchange over this grassland. The difference in gross primary production between the two years was not caused by the variation in annual precipitation. Instead, air temperature and the length of growing season had an important impact on annual gross primary production. Variation of annual ecosystem respiration was closely related to annual gross primary production and soil water content during the growing season.

Water and CO2 fluxes over semiarid alpine steppe and humid alpine meadow ecosystems on the Tibetan Plateau

Based on eddy covariance flux data from July 15, 2014, to December 31, 2015, the water and CO2 fluxes were compared over a semiarid alpine steppe (Bange, Tibetan Plateau) and a humid alpine meadow (Lijiang, Yunnan) on the Tibetan Plateau and its surrounding region. During the wet season, the evaporative fraction (EF) was strongly and linearly correlated with the soil water content (SWC) at Bange because of its sparse green grass cover. In contrast, the correlation between the EF at Lijiang and the SWC and the normalized difference vegetation index (NDVI) was very low because the atmosphere was close to saturation and the EF was relatively constant. In the dry season, the EF at both sites decreased with the SWC. The net ecosystem exchange (NEE) at Bange was largely depressed at noon, while this phenomenon did not occur at Lijiang. The saturated NEE at Bange was 24% of that at Lijiang. The temperature sensitivity coefficient of ecosystem respiration at Bange (1.7) was also much lower than that at Lijiang (3.4). The annual total NEE in 2015 was 21.8 and −230.0 g C m−2 yr−1 at Bange and Lijiang, respectively, and the NEE was tightly controlled by the NDVI at the two sites. The distinct differences in the water and CO2 fluxes at Bange and Lijiang are attributed to the large SWC difference and its effect on vegetation growth.

Sensitivity of soil organic matter decomposition to temperature at different depths in permafrost regions on the northern Qinghai‐Tibet Plateau

The temperature sensitivity coefficient (Q10) of soil organic matter decomposition is an important variable for global climate models. Permafrost regions contain large organic carbon pools. A deep core was taken in permafrost from the northern Qinghai‐Tibet Plateau (QTP) and exposed to increases in temperature below and above 0°C. The production of CO2 was related to the soil organic carbon (SOC) contents and stable carbon isotopes. Smaller values of δ13C‐SOC and δ13C‐CO2 showed that the release of CO2 was primarily from soil with large SOC contents. The sensitivities of soil organic matter (SOM) decomposition to temperature near to the permafrost table and in some permafrost layers were larger than those in other layers. In some layers, a temperature increase below 0°C had a greater effect on the decomposition of SOM than one above 0°C. The values of Q10 in active layers varied from 2.7 to 23.0, with a mean of 8.8. The values of Q10 were larger in the deeper layers; they varied from 1.6 to 49.4, with a mean of 20.8. This is because the degradation of permafrost is usually associated with an increase in temperature even when the soil is in a frozen state. Our results suggest that the large values of Q10 at depth under frozen conditions merit more consideration of the response of SOC to climate warming in future research.HighlightsThe sensitivity to temperature coefficient, Q10, is an important property for global climate models. The values of Q10 for soil organic matter decomposition were also large in deep layers. A temperature increase below 0°C has large effects on Q10. The large values of Q10 at depth under frozen conditions merit more consideration.

Temperature sensitivity of soil carbon dioxide and nitrous oxide emissions in mountain forest and meadow ecosystems in China

An incubation experiment was conducted at three temperature levels (8, 18 and 28 °C) to quantify the response of soil CO2 and N2O emissions to temperature in three ecosystems (pine forest, oak forest, and meadow) located in the Qinling Mountains of China, which are considered to be susceptible to disturbance and climate changes, especially global warming. The soil CO2 emission rates increased with temperature and decreased with soil depth; they were the highest in the oak forest (broadleaf forest) and were lower in the pine forest (coniferous forest) and the meadow ecosystem. However, there was no significant difference in the soil N2O emission rates among the three ecosystems. The temperature sensitivity of CO2 and N2O was higher in the forest than in the meadow ecosystem. The Q10 values (temperature sensitivity coefficient) for CO2 and N2O were 1.07–2.25 and 0.82–1.22, respectively, for the three ecosystems. There was also evidence that the CO2 and N2O emission rates were positively correlated. The soil characteristics exhibited different effects on CO2 and N2O emissions among different ecosystems at the three temperature levels. Moreover, the soil dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA) and nitrate (NO3−) were important factors for CO2 emissions, whereas the soil ammonium (NH4+) and pH were the major controllers of N2O emissions. Unexpectedly, our results indicated that CO2 emissions are more sensitive to increasing temperature than N2O, noting the different feedback of CO2 and N2O emissions to global warming in this region. The different responses of greenhouse gas emissions in different forest types and a meadow ecosystem suggest that it is critical to conduct a comprehensive investigation of the complex mountain forest and meadow ecosystem in the transitional climate zone under global warming. Our research results provide new insight and advanced understanding of the variations in major greenhouse gas emissions (CO2 and N2O) and soil characteristics in response to warming.