Infrared Gas Analyzer Research Articles

Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers

Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO2) fluxes (Fc_OP). Differences in net CO2 fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring Fc_OP has not been characterized yet. These IRGAs measure CO2 absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO2 density. This sensor-internal conversion is based on a slow-response thermistor air temperature measurement. Here, we test if the high-frequency temperature attenuation causes selectively systematic Fc_OP errors that scale with kinematic temperature fluxes. First, we examine the relationship between wintertime Fc_OP and kinematic temperature fluxes for eight northern ecosystems. Second, we investigate how residuals between Fc_OP and CO2 fluxes from co-located closed-path IRGAs (FC_CP) are related to kinematic temperature fluxes for three different ecosystem types (i.e., boreal forest, grassland, and irrigated cropland). We find that kinematic temperature fluxes, but not mean ambient air temperatures or CO2 flux regime, consistently determine the absolute magnitude of Fc_OP errors. This selectively systematic bias causes the most pronounced relative Fc_OP errors to occur when “true” CO2 fluxes are low and kinematic temperature fluxes are high (e.g., northern ecosystems during the winter). The smallest relative errors occur during periods with large “true” CO2 fluxes and low kinematic temperature fluxes. To address this bias, we replace the slow-response air temperature in the absorption-to-CO2 density conversion with a fast-response air temperature derived from sonic anemometer measurements. The use of the fast-response air temperature improves the agreement between half-hourly Fc_OP and FC_CP for all open- versus closed-path IRGA comparisons. Additionally, cumulative Fc_OP and Fc_CP sums are more comparable as differences drop from 63 %–13 % to 20 %–8 %. The improved IRGASON and EC150 performance enhances the ability and confidence to synthesize flux measurements across multiple sites including these two relatively new IRGAs.

PARTIÇÃO DA EVAPOTRANSPIRAÇÃO PARA UMA CULTURA DE MILHO

Crop transpiration is directly related to its production. Plant transpiration varies along the crop cycle and in most part of this cycle is the dominant component in evapotranspiration. There are several well-established techniques to estimate these components individually. Currently, the eddy covariance technique is widely used for measurements of evapotranspiration. However, this technique is unable to identify the flow of water between the surface and the atmosphere has its origin by evaporation from soil or plant transpiration. A new methodology based on the efficiency of water use by the plant is being used successfully. This technique determines how much water is transpired to each carbon molecule attached to the plant. This efficiency ratio is obtained by the difference of external and internal concentration on stomatal cavity of CO2 and H2O. In practice, external concentration of carbon and water is obtained from the infra-red gas analyzers used to obtain data in eddy covariance technique. In this work, the evapotranspiration for a maize crop in southern Brazil is partitioned and compared to the surface model AGRO-IBIS. Results show that the maximum development of the plant transpiration is approximately 70% of evapotranspiration.

New low-cost automated system of closed chambers to measure greenhouse gas emissions from the tundra

The northern high latitudes represent the world’s largest soil carbon reservoir. Due to the rapid warming in the Arctic, permafrost thawing is expected to lead to increased emissions of greenhouse gases (GHG). Therefore, quantifying these emissions has become very important in order to determine the feedback impacts of GHG release from permafrost on the global climate. However, permafrost GHG emissions are difficult to quantify because direct measurements with conventional methods are generally expensive and time-consuming, resulting in short-spanned experiments and limited number of measurements. In order to take continuous measurements of GHG emissions over long periods of time, we developed and tested an affordable automated system of four closed chambers equipped with low-cost sensors and open-source microcontrollers. We measured carbon dioxide concentrations with a low-cost CO2 sensor and compared it with an infrared gas analyzer (IRGA). Compared to the IRGA, the sensor overestimated fluxes by only 6%, making it a good alternative to conventional devices to measure CO2 concentrations. The chambers were compared to a commercial chamber (SRC-1, PP Systems) and results showed a 15% discrepancy between the two types of chamber. However, more laboratory testing is necessary to confirm the exact cause of the discrepancy. This low-cost system shows high potential and represents a good alternative to existing methods and apparatuses to measure soil CO2 emissions.

Temporal and spatial variation of soil respiration under mulching in a greenhouse cucumber cultivation

Abstract: The objective of this work was to determine the temporal and spatial variations of soil respiration (Rs) in a greenhouse, as well as the factors causing them, in a soil covered with different mulching types and cultivated with cucumber (Cucumis sativus). Four mulching treatments were applied to a soil cultivated with cucumber: CK, conventional practice without mulch; FM, plastic film mulch; CM, combined mulch of plastic film with wheat straw; and SM, wheat straw mulch. Rs was measured by a soil respiration chamber connected to a portable infrared gas analyzer, and the differences of Rs between mulchings were evaluated. Rs was significantly lower in the control than in the treatments with mulch. In addition, Rs was higher in the position on the soil near plants (5.4 μmol CO2 m-2 s-1) than in the positions between plants (4.7 μmol CO2 m-2 s-1) and rows (3.9 μmol CO2 m-2 s-1). Soil water content and temperature had an interacted effect on Rs. Cucumber root biomass and root vigor should also be incorporated as predictor variables for Rs in the succession crops, mainly for accurately estimating carbon cycling in agroecosystems in a greenhouse.

Effect of chamber enclosure time on soil respiration flux: A comparison of linear and non-linear flux calculation methods

One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre-deployment fluxes by linear regression techniques. Thus, usually the cumulative flux curve becomes downward concave due to the decreased gas diffusion rate. Non-linear models based on biophysical theory usually fit to such curvatures and may reduce the underestimation of fluxes. In this study, we examined the effect of increasing chamber enclosure time on SR flux rates calculated using a linear, an exponential and a revised Hutchinson and Mosier model (HMR). Soil respiration rates were measured with a closed chamber in combination with an infrared gas analyzer. During SR flux measurements the chamber was placed on fixed collars, and CO2 concentration in the chamber headspace were recorded at 1-s intervals for 45 min. Fluxes were measured in different soil types (sandy, sandy loam and organic soils), and for various manipulations (tillage, rain and drought) and soil conditions (temperature and moisture) to obtain a range of fluxes with different shapes of flux curves. The linear method provided more stable flux results during short enclosure times (few min) but underestimated initial fluxes by 15–300% after 45 min deployment time. Non-linear models reduced the underestimation as average underestimation was only about 10% after 45 min for regular flux curves. For irregular flux curves with a rapid increase in CO2 concentration immediately after chamber deployment it was shown that short enclosure times were prone to overestimation of pre-deployment fluxes, but this was mitigated by longer enclosure times (>10–15 min).

Responses and influencing factors of foliar photosynthetic characteristics of <italic>Larix gmelinii </italic>to changing environments

Investigating tree photosynthetic capacity is important for understanding the carbon cycles of terrestrial ecosystems and their responses and adaptation to climatic change. Dahurian Larch ( Larix gmelinii ) is one of the dominant tree species in Chinese boreal forests with a broad bio-geographic range under divergent habitats, and thus an ideal tree species for exploring tree adaptation to environment. In this study, we measured the foliar photosynthesis and associated physiological parameters of 30-year-old Dahurian larch trees from six provenances in a common garden at the Maoershan Forest Ecosystem Research Station in Northeast China for three years (2009–2011). The six provenances were located across the natural distribution range of the larch, spanning approximately 4° in latitude (48°–52°N), 5°C in mean annual temperature ( - 2.3–2.6°C), and 200 mm in mean annual precipitation (425–622 mm). To access the top canopy of the sampled trees, we constructed 15-m-high wooden scaffolds at the site. Three representative trees from each provenance were selected for the measurements per month from mid May to mid September. We measured three fully expanded sunlit fascicles on young short shoots at the top of the canopy of each tree in situ with an infrared gas analyzer. On non-rainy days, light and CO2 response curves were measured between 06:30 and 12:00 hours under optimal conditions. Our goal was to explore impacts of environmental changes on foliar photosynthetic characteristics of the larch and their driving factors. The main results were summarized as follows: (ⅰ) The leaf-area-based maximum net photosynthetic rate ( P max-a), dark respiratory rate ( R a), apparent quantum yield (AQY), maximum rate of carboxylation ( V max), maximum electron transport rate ( J max) and triose phosphate utilization rate (TPU) all increased significantly ( P T s) and aridity index (AI) of the seed-source original sites, while the light compensation point (LCP) and photorespiratory rate ( R p) showed an opposite trend. This suggests that the leaf photosynthetic characteristics genetically adapt to the original site conditions of the tree seed-sources, among which the temperature and precipitation are the major driving factors. (ⅱ) P max-a was positively correlated with AQY, V max, J max, TPU, and leaf nitrogen concentration, but negatively with LCP and R p ( P T s habitats had higher sensitivity of P max-a associated with other characteristics. (ⅲ) P max-a was significantly and positively correlated with 3-day mean temperature, mean monthly temperature, mean growing season temperature, 3-day mean relative humidity, and mean monthly precipitation of the common garden, while the R a showed opposite trends with the environmental factors except for the mean growing season temperature. This indicates that the leaf photosynthetic characteristics acclimate to the environmental conditions of the common garden. However, the trees from higher T s habitats had lower intercepts of the regression equations of P max-a associated with the environmental factors, and had the opposite trends for R a except for the mean growing season temperature. The results suggest that the relationships between foliar photosynthetic characteristics and environment are jointly controlled by both phenotypic acclimation to current site conditions and genotypic adaptation to the original environment of the seed-source. These findings provide insights on understanding the survival, reproduction and distribution of Dahurian larch to changing environments.

Atividade fotossintética de plantas cultivadas em solo contaminado com sulfentrazone

Objetivou-se com este trabalho, avaliar os efeitos do sulfentrazone sobre as características associadas à atividade fotossintética de Helianthus annus, Canavalia ensiformis, Dolichos lab lab e Arachis hypogaea consideradas espécies com potencial de remediação de solo contaminado por esse herbicida. O experimento foi conduzido em esquema fatorial 4 x 3 em delineamento inteiramente casualizado, com quatro repetições. O primeiro fator constou do cultivo das espécies H. annus, C. ensiformis, D. lab lab e A. hypogaea e o segundo de três doses (0, 250 e 500 g ha-1) de sulfentrazone aplicadas em pré-emergência. Após o preenchimento dos vasos com 6,0 kg de solo, classificado como Argissolo Vermelho-Amarelo, fez-se a irrigação e aplicou-se à superfície do solo o herbicida. Um dia após esta aplicação, procedeu-se a semeadura das espécies vegetais. Aos 40 dias após a emergência (DAE) das espécies vegetais, foram determinadas a condutância estomática (gs - mol m-1 s-1), a taxa de transpiração (E - mol H2O m-2 s-1), a concentração de CO2 na câmara subestomática (Ci - µmol mol-1), o gradiente de CO2 (ΔC - µmol mol-1) e a taxa fotossintética (A - µmol m-2 s-1). Essas avaliações foram realizadas utilizando-se um analisador de gases no infravermelho (IRGA). Aos 100 DAE das plantas foi coletada a parte aérea e determinada a matéria seca. Resíduos de sulfentrazone no solo podem afetar as variáveis fisiológicas estudadas, todavia, a produção de matéria seca da parte aérea dessas espécies não foi influenciada pela ação do herbicida, independentemente das doses aplicadas, indicando a tolerância das espécies ao sulfentrazone.

A simple method for in-situ assessment of soil respiration using alkali absorption

Lacking knowledge about the spatial heterogeneity of heterotrophic soil respiration (Rh) hampers the prediction of larger-scale soil CO2 efflux in patchy landscapes. The aim of this study was to establish a cost-efficient method for the rapid and simultaneous assessment of cumulative heterotrophic soil respiration (CO2) at different sample spots. For this purpose, we adapted the laboratory-based, fully-automated Respicond VIII respirometer (Respicond) to detect CO2 emission under field condition, installed the device in two temperate grasslands, and compared the Rh flux data with those obtained using the so-called dynamic chamber method with infrared gas analyzers (IRGA). The results revealed good agreement between both Rh measurements (Slope=0.89, R2=0.99). We conclude that adapting the Respicond for detection of CO2 under field conditions is principally feasible, thus providing a new tool for the simultaneous assessment of CO2 fluxes from different soil ecosystems.

Reduction of Quartz to Silicon Monoxide by Methane-Hydrogen Mixtures

The reduction of quartz was studied isothermally in a fluidized bed reactor using continuously flowing methane-hydrogen gas mixture in the temperature range from 1623 K to 1773 K (1350 °C to 1500 °C). The CO content in the off-gas was measured online using an infrared gas analyzer. The main phases of the reduced samples identified by XRD analysis were quartz and cristobalite. Significant weight loss in the reduction process indicated that the reduction products were SiO and CO. Reduction of SiO2 to SiO by methane starts with adsorption and dissociation of CH4 on the silica surface. The high carbon activity in the CH4-H2 gas mixture provided a strongly reducing condition. At 1623 K (1350 °C), the reduction was very slow. The rate and extent of reduction increased with the increasing temperature to 1723 K (1450 °C). A further increase in temperature to 1773 K (1500 °C) resulted in a decrease in the rate and extent of reduction. An increase in the gas flow rate from 0.4 to 0.8 NL/min and an increase in the methane content in the CH4-H2 gas mixture from 0 to 5 vol pct facilitated the reduction. Methane content in the gas mixture should be maintained at less than 5 vol pct in order to suppress methane cracking.

Dimensioning IRGA gas sampling systems: laboratory and field experiments

Abstract. Both laboratory and field experiments were carried out in order to define suitable configuration ranges for the gas sampling systems (GSSs) of infrared gas analyzers (IRGAs) used in eddy covariance measurements.In the laboratory, an original dynamic calibration bench was developed in order to test the frequency attenuation and pressure drop generated by filters. In the field, three IRGAs of the same type equipped with different filters or different rain caps were installed and run and the real frequency response of the complete setup was tested. The main results are as follows. – Filters may have a strong impact on the pressure drop in the GSS and this impact increases with flow rate. – Conversely, no impact of the tested filters on cut-off frequency was found, GSSs with and without filters presenting similar cut-off frequencies. – The main limiting factor of cut-off frequency in the field was found to be the rain cap design. In addition, the impact of this design on pressure drop was also found to be noteworthy.

Optimization of an enclosed gas analyzer sampling system for measuring eddy covariance fluxes of H<sub>2</sub>O and CO<sub>2</sub>

Abstract. Several initiatives are currently emerging to observe the exchange of energy and matter between the earth's surface and atmosphere standardized over larger space and time domains. For example, the National Ecological Observatory Network (NEON) and the Integrated Carbon Observing System (ICOS) are set to provide the ability of unbiased ecological inference across ecoclimatic zones and decades by deploying highly scalable and robust instruments and data processing. In the construction of these observatories, enclosed infrared gas analyzers are widely employed for eddy covariance applications. While these sensors represent a substantial improvement compared to their open- and closed-path predecessors, remaining high-frequency attenuation varies with site properties and gas sampling systems, and requires correction. Here, we show that components of the gas sampling system can substantially contribute to such high-frequency attenuation, but their effects can be significantly reduced by careful system design. From laboratory tests we determine the frequency at which signal attenuation reaches 50 % for individual parts of the gas sampling system. For different models of rain caps and particulate filters, this frequency falls into ranges of 2.5–16.5 Hz for CO2, 2.4–14.3 Hz for H2O, and 8.3–21.8 Hz for CO2, 1.4–19.9 Hz for H2O, respectively. A short and thin stainless steel intake tube was found to not limit frequency response, with 50 % attenuation occurring at frequencies well above 10 Hz for both H2O and CO2. From field tests we found that heating the intake tube and particulate filter continuously with 4 W was effective, and reduced the occurrence of problematic relative humidity levels (RH > 60 %) by 50 % in the infrared gas analyzer cell. No further improvement of H2O frequency response was found for heating in excess of 4 W. These laboratory and field tests were reconciled using resistor–capacitor theory, and NEON's final gas sampling system was developed on this basis. The design consists of the stainless steel intake tube, a pleated mesh particulate filter and a low-volume rain cap in combination with 4 W of heating and insulation. In comparison to the original design, this reduced the high-frequency attenuation for H2O by ≈ 3∕4, and the remaining cospectral correction did not exceed 3 %, even at high relative humidity (95 %). The standardized design can be used across a wide range of ecoclimates and site layouts, and maximizes practicability due to minimal flow resistance and maintenance needs. Furthermore, due to minimal high-frequency spectral loss, it supports the routine application of adaptive correction procedures, and enables largely automated data processing across sites.

Industrial SO<sub>2</sub> emission monitoring through a portable multichannel gas analyzer with an optimized retrieval algorithm

Abstract. SO2 variability over a large concentration range and interferences from other gases have been major limitations in industrial SO2 emission monitoring. This study demonstrates accurate industrial SO2 emission monitoring through a portable multichannel gas analyzer with an optimized retrieval algorithm. The proposed analyzer features a large dynamic measurement range and correction of interferences from other coexisting infrared absorbers such as NO, CO, CO2, NO2, CH4, HC, N2O, and H2O. The multichannel gas analyzer measures 11 different wavelength channels simultaneously to correct several major problems of an infrared gas analyzer including system drift, conflict of sensitivity, interferences among different infrared absorbers, and limitation of measurement range. The optimized algorithm uses a third polynomial instead of a constant factor to quantify gas-to-gas interference. Measurement results show good performance in the linear and nonlinear ranges, thereby solving the problem that the conventional interference correction is restricted by the linearity of the intended and interfering channels. The results imply that the measurement range of the developed multichannel analyzer can be extended to the nonlinear absorption region. The measurement range and accuracy are evaluated through experimental laboratory calibration. Excellent agreement was achieved, with a Pearson correlation coefficient (r2) of 0.99977 with a measurement range from approximately 5 to 10 000 ppmv and a measurement error of less than 2 %. The instrument was also deployed for field measurement. Emissions from three different factories were measured. The emissions of these factories have been characterized by different coexisting infrared absorbers, covering a wide range of concentration levels. We compared our measurements with commercial SO2 analyzers. Overall, good agreement was achieved.

Decarburisation Effect on Hardened Strip Steel Fastening Components

Heat treatment is widely used for high reliability fastening components such as buckles and brackets. The current study focuses on mass production of safety components which are fineblanked from sheet metal, austempered and chromium electroplated. Electroplating together with stamping defects may lead to unexpected brittle failure of the component. It is widely known that during austenitisation, decarburisation could avoid brittle failure and, therefore, slight decarburisation is recommended. There is little information how much mass production is influenced by decarburisation and where the limits are. The current study has two goals. The first one focuses on the extent of decarburisation effect on the part properties, and the second aims to find the optimum furnace setting for the product type used in the study. Also, it is necessary to choose a reliable decarburisation control method for austempered components. The effect on material grades was analyzed by using three steel alloys with carbon content of 0.37 wt.%, 0.47 wt.% and 0.62 wt.%. The specimens were austempered to hardness 45 – 51 HRC under endothermic protective atmosphere. To gain different decarburisation levels, two gas set-ups were used. Infrared gas analyzer was used to measure CO and CO2 content in the furnace gas. Three characteristics of the specimens were evaluated: hardness, rupture strength and brittleness. The depth of the decarburisation was determined by three different approaches according to standard EN ISO 3887. Based on the results, the spectrographic method is the most reliable for determining the depth of decarburisation. This study reveals that higher surface decarburisation has a positive effect on the ductility and no effect on the rupture strength of the component. The material with carbon content of 0.62 wt.% is the most sensitive to decarburisation. During mass production, the inaccuracy of hardness measuring raises which results in the inaccuracy of salt bath temperature regulation. For the used thermal cycle, the furnace gas carbon potential 0.30 – 0.40 has to be used to ensure expected performance of fastening products.

Mycorrhizal contribution to soil respiration in an apple orchard

Soil respiration (Rsoil) partitioning into its components is pivotal to understand C cycling in ecosystems. Notwithstanding the importance of mycorrhizal fungi in the belowground C cycle, their respiration (Rmyc) is poorly studied in agricultural ecosystems. In this study, we applied a modified trenching method and the 13C natural abundance technique to distinguish Rmyc from root respiration (Rroot) and from the respiration due to soil organic matter (SOM) degradation (Rsom) in an apple orchard (Malus domestica Borkh.) located in Northern Italy. Membranes with different mesh size were used to physically exclude roots or mycorrhizae from soil cores with a different δ13C than the orchard average value. The CO2 efflux from soil cores was determined with an infrared gas analyser, and isotopic measurements were performed on the soil-emitted CO2. The different Rsoil components were determined both by difference and by the isotopic mass balance. Mycorrhizal contribution to soil respiration (11±6%) was of similar magnitude to that of roots (12±4%) while Rsom accounted for 73±3% of Rsoil. In presence of apple roots, respiration of SOM and mycorrhizae (Rsom+myc) significantly increased in late summer and autumn, likely because of a priming effect of roots on SOM degradation or to a stimulation of mycorrhizal respiration. Our results suggest that respiration of mycorrhizal fungi can significantly contribute to Rsoil, and need to be considered to correctly partition soil respiration. Furthermore, as roots increased Rsom+myc, the root exclusion method for soil respiration partitioning may overestimate Rroot.

How do the heterotrophic and the total soil respiration of an oil palm plantation on peat respond to nitrogen fertilizer application?

Increasing oil palm (OP) plantation establishment on tropical peatlands over the last few decades has major implications for the global carbon (C) budget. This study quantified total and heterotrophic soil carbon dioxide (CO2) emissions in an industrial OP plantation (7year old, 149treesha−1) on peat located in the eastern coast of the Sumatra Island (Jambi district), Indonesia, after two doses of nitrogen (N) fertilizer application at rates typical of local practice. The first dose applied in March 2012 (first Fertilization event FE) consisted of 0.5kg urea per palm (equivalent to 371kgNha−1 at the base of the palm which when extrapolated across the plantation was 35kgNha−1) and the second dose applied in February 2013 (second FE) amounted to 1kg urea per palm. Soil CO2 fluxes were measured using an infrared gas analyzer (IRGA) in dark closed chambers. The measurements were made daily from 1day before to 7days after fertilizer application. Soil heterotrophic respiration (Rh) and total soil respiration (Rs) were measured in trenched plots (where root respiration was excluded) and non-trenched plots, respectively. Concomitant with CO2 flux measurements, air and soil temperatures, rainfall and the water table level were measured. To estimate the fertilizer effect during the different times of the day, CO2 fluxes were monitored every 3h during a 24h period on days 2 and 3 after fertilizer application during the second FE. Shortly after fertilizer application, substantial pulses of CO2 were detected in the IRGA chambers where the fertilizer was applied. Even though the fertilized area represents 9.4% of the plantation area only, the impact of fertilizer application at the plantation scale on CO2 fluxes was noteworthy when compared to non-fertilized control treatments. The Rs was 36.9kgCO2–Cha−1 (7days)−1 greater in the fertilized than in the non-fertilized plots after the first FE but no enhancement was observed after the second FE (−72.2kgCO2–Cha−1 7days−1). The Rh was 340.5 and 98.9kgCO2–Cha−1 (7days)−1 greater in the fertilized than in the non-fertilized plots after the first and second FE, respectively. The larger CO2 flux enhancement in Rh as compared to Rs may be the result of fertilizer uptake by the palm roots in the un-trenched plots, while in the trenched ones where roots were absent, microorganisms used the fertilizer to accelerate soil organic matter mineralization. Although the response of Rh to N addition and the priming effect were high as compared to results in the literature, the impacts were short-term only and may not have implications on the annual C budget of the plantation.

Estimation of gas exchange parameters in backcross introgressed lines of rice (Oryza sativaL.) with different combinations of drought qtls

The present investigation was carried out to study the gas exchange parameters in backcross inbred lines of ‘Improved White Ponni’ (IWP) introgressed with different drought yield QTLs and their parents raised under control and stress conditions. Various gas exchange parameters and single plant yield were observed using portable photosynthetic system (infra red gas analyser -IRGA). Among the genotypes, three combination of QTL line IWP-4-2 recorded significantly higher photosynthetic rate (22.97 μ mol CO2 m−2 s−1), stomatal conductance (0.36 mol H2O m−2 s−1), transpiration rate (6.25 mmol H2O m−2 s−1), internal CO2 concentration (240.82) ratio between internal and atmospheric CO2 concentration (0.25) and single plant yield (15.11) which was on par with the tolerant parent Apo (an high yielding indica cultivar moderately tolerant to drought stress) under severe moisture stress regime. Overall study clearly revealed that, the performance of introgressed line with three drought QTLs (IWP-4-2) was better than two drought QTL introgressed lines of IWP-1-52 and IWP-1-57. Results from graphical genotyping using three foreground and 36 polymorphic background markers revealed that, the three QTL introgressed line IWP-4-2 had 72.20% genome recovery from Improved White Ponni, 13.89% from APO and 13.89% heterozygous region.

施氮对湿地松（Pinus elliottii）林土壤呼吸和相关因子的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 施氮对湿地松(Pinus elliottii)林土壤呼吸和相关因子的影响 DOI: 10.5846/stxb201311192767 作者: 作者单位: 中南林业科技大学,国家林业局;中南林业科技大学,广西壮族自治区林业科学研究院,城市森林生态湖南省重点实验室;中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学,南方林业生态应用技术国家工程实验室;中南林业科技大学,城市森林生态湖南省重点实验室;中南林业科技大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项(201404316);湖南省自然科学创新研究群体基金(湘基金委字[2013]7号);湖南省高校创新平台开放基金项目(12K070);国家林业局软科学研究项目(2013-R09);城市森林生态湖南省重点实验室资助 The effect of nitrogen addition on soil respiration and associated factors in Pinus elliottii forest Author: Affiliation: Central South University of Forestry and Technology,Central South University of Forestry and Technology,Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology,National Engineering Laboratory for Applied Technology of Forestry Ecology in South China,Changsha,;Central South University of Forestry and Technology,Key laboratory of Urban Forest Ecology of Hunan Province;Central South University of Forestry and Technology 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:人类活动引起陆地生态系统氮输入水平持续升高,对全球碳循环产生影响。为探究氮素对土壤呼吸的影响,2010年6月至2012年1月,采用氮添加试验对亚热带湿地松林的土壤呼吸进行了研究。试验共设置4种氮添加水平:对照CK,0 g m-2 a-1;低氮LN,5 g m-2 a-1;中氮MN,15 g m-2 a-1;高氮HN,30 g m-2 a-1;每月上、下旬采用Li-cor 8100测定土壤呼吸速率。结果表明:(1)氮添加对土壤呼吸有着显著的抑制作用,LN、MN和HN处理的土壤呼吸年累积量较CK处理分别降低了26.6%、23.7%和29.5%,而施氮处理间的土壤呼吸无显著差异;(2)林分生长期间(6-9月),施氮第1年的土壤呼吸所受抑制作用显著高于第2年同期的水平,显示施氮对土壤呼吸的影响随时间的推移而降低;(3)湿地松林土壤呼吸存在明显的季节动态,最大值出现在8月(356.32 mgCO2 m-2 h-1),最小值出现在1月(99.12 mg CO2 m-2 h-1),施氮处理并不改变土壤呼吸的季节性变化规律;(4)CK处理林分中,土壤呼吸与土壤温度间存在极显著的指数关系,而与土壤湿度无显著相关。施氮处理没有改变土壤呼吸与土壤温度之间的相互关系,但抑制了土壤呼吸的温度敏感性(Q10);(5)施氮处理显著减少了林分凋落物量、土壤微生物碳、氮量,并轻微抑制了细根生物量,这些改变导致了土壤呼吸的下降。上述结果表明施氮会显著抑制亚热带湿地松林的土壤呼吸速率,而这种抑制作用将随着时间的推移而降低。 Abstract:Human activities have raised nitrogen input to terrestrial ecosystems and influenced the global carbon cycle. To determine how soil respiration responds to nitrogen addition, a simulated nitrogen deposition experiment was conducted in Pinus elliottii forest in a subtropical zone in China from June 2010 to January 2012. Four-levels of N treatment-control check(CK,0 g m-2 a-1)、low nitrogen(LN, 5 g m-2 a-1)、medium nitrogen(MN, 15 g m-2 a-1) and high nitrogen(HN, 30 g m-2 a-1)-were applied and infrared gas analyzer techniques were used to quantify the soil respiration twice a month. The results showed that(1) soil respiration exhibited a clearly seasonal pattern, with the highest rates found in the August(356.32 mg CO2 m-2 h-1) and the lowest rates in January(99.12 mg CO2 m-2 h-1), and that nitrogen addition significantly depressed soil respiration. The soil annual accumulative soil respiration in the LN, MN, and HN treatments was 26.56%, 23.72%, and 29.54% lower, respectively, than CK treatment, but there is no significant difference between the nitrogen addition treatments. Furthermore, the inhibitory action weakened over time. Analysis of the soil respiration rate from June to September showed that(1) the inhibitory effect of nitrogen addition in the first year was weaker than that in the second year;(2) there was no strong diurnal soil respiration pattern; during daytime, nitrogen addition did not repress of soil respiration; and(3) soil respiration rates showed a significant positive exponential relationship with soil temperature at 5 cm depth. Soil temperature was the dominant driving factor and nitrogen addition reduced the Q10 values. Our results suggest that soil respiration declined in response to N addition in subtropical Pinus elliottii forest. 参考文献 相似文献 引证文献

Evaluation of response of lettuce (Lactuca sativa L.) to temperature and light stress

The aim of the study was to assess the effect of irrigation water temperature and shading on the rate of photosynthesis and transpiration in four varieties of lettuce (<em>Lactuca sativa</em> L.) – green foliage (‘Salakis’ and ‘Estony’) and red foliage (‘Lollo Rossa’ and ‘Nika’). During the production of seedlings in the greenhouse, two irrigation water temperature regimes (12 and 20°C) were applied. After transplanting in the field plants were grown under three lighting systems (100, 70, and 50% of lighting in the open). The rates of photosynthesis and transpiration were measured at the end of the greenhouse period and 14 days after shading in the field using a Li 6400 infrared gas analyzer. In most varieties, cooling of the irrigation water was not found to have an effect on the rate of photosynthesis. Plants of all the varieties responded to the decrease in irrigation water temperature and to strong shading by reducing transpiration and increasing the water use efficiency. The ‘Salakis’ and ‘Estony’ plants have shown the best adaptability to the changing conditions and therefore they could be used successfully in the practice of extending vegetative growth.

DME/Methane混合燃料を用いた過給HCCI燃焼特性に関する研究

An investigation was made of the fundamental combustion characteristics of a supercharged Homogenous Charge Compression Ignition (HCCI) engine operating on a gaseous fuel blend of dimethyl ether and methane. Besides measuring the in-cylinder pressure, spectroscopic techniques were used to measure light absorbance and light emission intensity. Exhaust gas samples were also analyzed with a Fourier transform infrared gas analyzer. The experimental results revealed that varying the input heat energy and the mixing ratios of the gaseous fuels caused the in-cylinder pressure to rise sharply, making stable engine operation difficult. However, it was found that applying supercharging while keeping the input heat energy constant moderated the pressure rise during combustion, though the in-cylinder pressure rose overall. As a result, that made it possible to avoid knocking and also to obtain cleaner exhaust emissions. Consequently, the results of this study demonstrate that applying supercharging according to the engine load is a key factor in controlling HCCI combustion.

Cadmium tolerance in Schinus molle trees is modulated by enhanced leaf anatomy and photosynthesis

Low concentrations of cadmium cause anatomical responses in leaf chlorenchyma enhancing Schinus molle photosynthesis and tolerance. This work is aimed to evaluate the effects of cadmium (Cd) on leaf anatomy and photosynthesis in Schinus molle, a species that can cope with harsh environments. Seven-month-old S. molle plants were exposed over 90 days to varying Cd concentrations (0, 10, 20, 50, 125 or 250 µM using Cd(NO3)2 as the Cd source). The plants were placed in vases containing washed sand and vermiculite as the substrate and nutrient solution. Throughout the experiment, the substrate was maintained at field capacity, and the nutrient solution was replaced at 15-day intervals. After 90 days, leaves were collected and processed for anatomical analysis using typical plant microtechniques. In addition, plant growth, photosynthesis, chlorophyll content and A/Ci curve were evaluated using an infrared gas analyzer. S. molle growth was not affected by Cd. Lower Cd concentrations (10 and 20 µM) resulted in greater net photosynthesis, stomatal conductance and density, Vcmax, Jmax and mesophyll thickness. However, Cd concentrations of 50 µM or greater resulted in a reduction of most of the evaluated characteristics to levels close to control. All of the tested Cd concentrations resulted in reduced chlorophyll content and stomatal size. Therefore, the effect of Cd in a tolerant species such as S. molle is concentration dependent, and at low Cd concentrations, these plants can cope with the toxicity by adjusting leaf structure and function.