Assessing the performance of the photo‐acoustic infrared gas monitor for measuring CO2, N2O, and CH4 fluxes in two major cereal rotations

Research on greenhouse gas (GHG) fluxes has predominantly focused on subtropical soils, with far less attention given to emissions from tree stems. In particular, year-long simultaneous measurements of both soil and tree stem fluxes in these forests are lacking, and data on standing dead trees is exceptionally scarce. We determined the dynamics of standing dead and live tree stems, and soil CH4, N2O and CO2 fluxes in a subtropical forest. We determined GHG fluxes from standing dead and live tree stems with three different tree heights (10 cm, 50 cm and 150 cm) of Cunninghamia lanceolata from January 2023 to December 2024 and subjected to analysis by gas chromatography. Measurements of environmental parameters were conducted in tandem with those of fluxes and xylem sap flow. Live tree stems contributed less to the annual GHG dynamics than standing dead trees. Live and standing dead tree stems generally acted as net annual sources of CH4, N2O, and CO2. Tree stem GHG fluxes decreased with decreasing precipitation. Soil was a sink of CH4, but a net CO2 and N2O source. Isolated emission peaks dominated the temporal dynamics of stem CH4, N2O, and CO2 fluxes and significantly contributed to the net annual fluxes. The CH4, N2O, and CO2 efflux from both live and standing dead tree stems exhibited a similar seasonal trend. The status (live or dead) and height of the trees significantly influenced stem GHG dynamics. During the study, CH4 emissions from tree stems (across different heights and precipitation conditions) offset an estimated 55.61~60.03% of the soil's CH4 sink capacity. Here, we demonstrate for the first time a strong correlation between stem greenhouse gas fluxes and sap flow in subtropical forests. The stem fluxes of CH4 in live and standing dead trees represented a combination of soil-derived and stem-produced methane, whereas CO2 and N2O fluxes were primarily soil-derived.

Context Conversion of grasslands to croplands can usually result in the degradation of soils and increased greenhouse gas (GHG) emissions such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, little is known about the impacts of grassland conversion to recently tilled croplands on soils and GHG fluxes. Aims A field experiment was established in 2016 to evaluate the impacts of grassland conversion to tilled cropland under different landscape positions (upslope, backslope, and footslope) on select soil properties and soil GHG fluxes. Key results The findings showed that the grassland conversion significantly increased soil bulk density and electrical conductivity but reduced pH and total nitrogen (TN). The conversion impacted soil biome community grassland and tilled croplands. The landscape position significantly impacted soil pH (footslope < upslope) and TN (footslope > upslope). The grassland conversion significantly decreased soil CO2 fluxes, but increased soil CH4 and N2O fluxes. The landscape position significantly impacted soil CO2 (footslope > upslope and backslope) and CH4 (upslope > footslope and backslope) fluxes for some periods. Soil CO2 and N2O fluxes generally followed upward and downward trends over time, respectively. Conclusions These results indicate that grassland conversion was able to lose soil N, increase soil compaction, acidity, salts, and soil N2O and CH4 fluxes, and decrease the diversity of abundant genera and CO2 fluxes. Footslope increased TN, soil acidity, CO2, and CH4 fluxes, compared with upslope and backslope. CO2 fluxes under grassland and tilled cropland significantly increased over time, whereas N2O fluxes under grassland significantly reduced. Implications Conversion of grassland to tilled cropland significantly impacted on sol quality. It caused a loss in soil N and increased soil compaction, acidity and salts. Grassland conversion also decreased the abundance and diversity soil microbiome.

No-till farming and greenhouse gas fluxes: Insights from literature and experimental data

CO2, CH4 and N2O flux changes in degraded grassland soil of Inner Mongolia, China

The invasions of the alien species such as Spartina alterniflora along the northern Jiangsu coastlines have posed a threat to biodiversity and the ecosystem function. Yet, limited attention has been given to their potential influence on greenhouse gas (GHG) emissions, including the diurnal variations of GHG fluxes that are fundamental in estimating the carbon and nitrogen budget. In this study, we examined the diurnal variation in fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from a S. alterniflora intertidal flat in June, October, and December of 2013 and April of 2014 representing the summer, autumn, winter, and spring seasons, respectively. We found that the average CH4 fluxes on the diurnal scale were positive during the growing season while negative otherwise. The tidal flat of S. alterniflora acted as a source of CH4 in summer (June) and a combination of source and sink in other seasons. We observed higher diurnal variations in the CO2 and N2O fluxes during the growing season (1 536.5 mg CO2 m–2 h–1 and 25.6 μg N2O m–2 h–1) compared with those measured in the non-growing season (379.1 mg CO2 m–2 h–1 and 16.5 μg N2O m–2 h–1). The mean fluxes of CH4 were higher at night than that in the daytime during all the seasons but October. The diurnal variation in the fluxes of CO2 in June and N2O in December fluctuated more than that in October and April. However, two peak curves in October and April were observed for the diurnal changes in CO2 and N2O fluxes (prominent peaks were found in the morning of October and in the afternoon of April, respectively). The highest diurnal variation in the N2O fluxes took place at 15:00 (86.4 μg N2O m–2 h–1) in June with an unimodal distribution. Water logging in October increased the emission of CO2 (especially at nighttime), yet decreased N2O and CH4 emissions to a different degree on the daily scale because of the restrained diffusion rates of the gases. The seasonal and diurnal variations of CH4 and CO2 fluxes did not correlate to the air and soil temperatures, whereas the seasonal and diurnal variation of the fluxes of N2O in June exhibited a significant correlation with air temperature. When N2O and CH4 fluxes were converted to CO2-e equivalents, the emissions of N2O had a remarkable potential to impact the global warming. The mean daily flux (MF) and total daily flux (TDF) were higher in the growing season, nevertheless, the MF and TDF of CO2 were higher in October and those of CH4 and N2O were higher in June. In spite of the difference in the optimal sampling times throughout the observation period, our results obtained have implications for sampling and scaling strategies in estimating the GHG fluxes in coastal saline wetlands.

IntroductionFarmlands are key sources of greenhouse gas (GHG) emissions, which are susceptible to changes in precipitation regimes. The soils of seasonal fallow contribute approximately half of annual GHG emissions from farmlands, but the effect of precipitation frequency on soil GHG emissions from seasonal fallow croplands remains virtually unknown.Materials and MethodsWe conducted a microcosm study to evaluate the response of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from typical paddy and upland soils to the changes in watering frequency simulating precipitation scenarios of subtropical regions during seasonal fallow. We also analyzed changes of soil properties and biotic characteristics associated with GHG emissions, including abundances of soil denitrifiers (nirK, nirS, nosZI and nosZII genes), methanotrophs (pmoA gene) and methanogens (mcrA gene) to altered watering frequency.ResultsIncreased watering frequency led to overall increases in soil N2O and CO2 fluxes compared with low frequency. Compared with low frequency, high watering frequency decreased CH4 flux from the paddy soil by 3.5 times, while enhanced CH4 flux from the upland soil by 60%. Furthermore, the increased watering frequency had positive effects on cumulative N2O and CO2 fluxes from the upland soil, whereas no similar trend was observed for the paddy soil. Hierarchical partitioning analyses showed that N2O fluxes from the paddy soil were mostly related to nitrogen availability, and mcrA gene abundance had more than 90% of relative independent effects on CH4 and CO2 fluxes from the paddy soil. For the upland soil, nosZ (60.34%), pmoA (53.18%) and nir (47.07%) gene abundances were important predictors of N2O, CH4 and CO2 fluxes, respectively.ConclusionOur results demonstrate that increased watering frequency facilitates GHG emissions by changing soil properties and functional gene abundances. These findings provide new insights into GHG fluxes from seasonal fallow croplands in response to altered precipitation patterns.

The study characterized the temporal and spatial variability in greenhouse gas (GHG) fluxes (CO2, CH4, and N2O) between December 2020 and November 2021 and their regulating drivers in the subtropical wetland of the Indian Himalayan foothill. Five distinct habitats (M1-sloppy surface at swamp forest, M2-plain surface at swamp forest, M3-swamp surface with small grasses, M4-marshy land with dense macrophytes, and M5-marshy land with sparse macrophytes) were studied. We conducted in situ measurements of GHG fluxes, microclimate (AT, ST, and SMC(v/v)), and soil properties (pH, EC, N, P, K, and SOC) in triplicates in all the habitat types. Across the habitats, CO2, CH4, and N2O fluxes ranged from 125 to 536mgm-2h-1, 0.32 to 28.4mgm-2h-1, and 0.16 to 3.14mgm-2h-1, respectively. The habitats (M3 and M5) exhibited higher GHG fluxes than the others. The CH4 flux followed the summer > autumn > spring > winter hierarchy. However, CO2 and N2O fluxes followed the summer > spring > autumn > winter. CO2 fluxes were primarily governed by ST and SOC. However, CH4 and N2O fluxes were mainly regulated by ST and SMC(v/v) across the habitats. In the case of N2O fluxes, soil P and EC also played a crucial role across the habitats. AT was a universal driver controlling all GHG fluxes across the habitats. The results emphasize that long-term GHG flux monitoring in sub-tropical Himalayan Wetlands has become imperative to accurately predict the near-future GHG fluxes and their changing nature with the ongoing climate change.

Greenhouse gas (CO2, CH4, N2O) emissions from soils following afforestation in central China

Water table management with controlled drainage and subsurface-irrigation (SI) has been identified as a Beneficial Management Practice (BMP) to reduce nitrate leaching in drainage water. It has also been shown to increase crop yields during dry periods of the growing season, by providing water to the crop root zone, via upward flux or capillary rise. However, by retaining nitrates in anoxic conditions within the soil profile, SI could potentially increase greenhouse gas (GHG) fluxes, particularly N2O through denitrification. This process may be further exacerbated by high precipitation and mineral N-fertilizer applications very early in the growing season. In order to investigate the effects of water table management (WTM) with nitrogen fertilization on GHG fluxes from corn (Zea mays) agro-ecosystems, we conducted a research study on a commercial farm in south-western Quebec, Canada. Water table management treatments were: free drainage (FD) and controlled drainage with subsurface-irrigation. GHG samples were taken using field-deployed, vented non-steady state gas chambers to quantify soil CO2, N2O and CH4 fluxes weekly. Our results indicate that fertilizer application timing coinciding with intense (≥24 mm) precipitation events and high temperatures (>25 °C) triggered pulses of N2O fluxes, accounting for up to 60% of cumulative N2O fluxes. Our results also suggest that splitting bulk fertilizer applications may be an effective mitigation strategy, reducing N2O fluxes by 50% in our study. In both seasons, pulse GHG fluxes mostly occurred in the early vegetative stages of the corn, prior to activation of the subsurface-irrigation. Our results suggest that proper timing of WTM mindful of seasonal climatic conditions has the potential to reduce GHG emissions.

Forest soils are recognized as sources and sinks of greenhouse gases (GHG) (CO2, CH4, N2O), but there are limited data quantifying the magnitude of GHG fluxes at the soil-atmosphere interface across a range of landscape hydrogeomorphic conditions. In our study, GHG fluxes were measured in a forested watershed across a range of hydrogeomorphic locations (wetlands, hillslopes, riparian zones, etc) and evaluated in relation to temperature, antecedent flow conditions, and stream chemistry to help develop strategies to scale GHG emissions from the point scale to the watershed scale. Mean study period CO2 fluxes (0.61 to 2.89 gCm-2d-1) were positive at all sites, with larger fluxes occurring in well-drained soils. Negative fluxes (CH4 sinks) were found at the hillslope and lowland sites, while the wetland was a large source of CH4 emissions at the watershed scale. Mean CH4 fluxes ranged from -2.53 to 330.34 mgCm-2d-1. Nitrous oxide fluxes were low relative to other GHG fluxes (in terms of CO2 equivalent) and ranged between -0.72 to 0.70 mgNm-2d-1. Although carbon dioxide fluxes were positively correlated to soil temperature at all locations, CH4 and N2O fluxes were not significantly related to temperature, antecedent flow conditions, or stream chemistry at the watershed scale. However, strong differences in CO2 and CH4 fluxes related to landscape geomorphology were observed, and exceeded the magnitude of seasonal variations for CO2 and CH4 fluxes, suggesting that landscape hydrogeomorphology was likely a stronger predictor of GHG fluxes at the watershed scale than temperature and stream chemistry variables, at least within the confine of one watershed. In lieu of statistical approaches relying on environmental variables to predict GHG fluxes at the watershed scale, geomorphological approaches, potentially coupled with seasonal comparisons of GHG fluxes in each land class, might therefore be a promising research avenue to provide solid watershed wide estimates of GHG fluxes.

Biogeochemical processes within and across ecosystems are core to understand the functioning of terrestrial ecosystems, i.e., forests and agroecosystems, in particular under changing environmental conditions. Measurements are necessary at multiple scales, e.g., for forests at soil, forest floor, tree, canopy, and forest ecosystem scales, using methodology from many different disciplines. Data should be available in high temporal resolution, preferentially for long time periods, to quantify and understand short-term responses to environmental drivers and management, but also to detect and identify long-term responses to climate change. The SwissFluxNet is a network of six long-term research sites in Switzerland with ecosystem-scale eddy-covariance (EC) measurements of biosphere-atmosphere greenhouse gas (GHG) exchange (i.e., CO2, H2O vapor, CH4, N2O; Fig. 1). The Swiss FluxNet offers exactly these opportunities, namely long-term, high-temporal resolution GHG flux data and serves as a research platform for many other studies and research programs. It covers the major land-use types in Switzerland: forest (mixed deciduous: Lägeren, CH-Lae; evergreen: Davos, CH-Dav), grassland (Chamau, CH-Cha; Früebüel, CH-Fru; Alp Weissenstein, CH-Aws), and cropland (Oensingen, Ch-Oe2), and is complemented by project-based flux stations which run for 2-4 years (currently, two below-canopy stations in the two forest sites, one young forest plantation, and two cropland sites). Thus, including data of 2024, we provide 129 site-years of continuous GHG flux measurements to the scientific community (19-28 years per site, and continuously growing…), since all data are open access and have been downloaded from FLUXNET and ICOS over 35'250 times between November 2016 and December 2024. In the talk, we will focus on the two forest sites, Davos and Lägeren. At Davos, above-canopy EC flux measurements of CO2 and H2O vapor started in 1997; measurements of above-canopy CH4 and N2O fluxes were carried out between 2016 and 2023 and complemented by below-canopy flux measurements of CO2 and H2O vapor (since 2021) as well as of CH4 (since 2023). Data on forest floor CO2, N2O and CH4 fluxes, measured automatically by chambers, tree phenology, sap flow and stem diameter changes are available for many years as well. Since 2019, Davos is an ICOS RI Class 1 Ecosystem station, where highest standards apply. At Lägeren, EC flux measurements of CO2 and H2O vapor are available since 2004, complemented by below-canopy flux measurements of CO2 and H2O vapor since 2014 as well as by phenology, soil respiration and tree ecophysiology measurements. At both sites, meteorological (above and within the canopy) as well as soil climate variables (soil profiles, 0 to 60/80 cm soil depth) are recorded continuously as well. Thus, measurements from multiple scales for long time periods allow studying short- and long-term responses to changing environments at both forest sites. We will provide selected highlights from almost 50 site-years of measurements, about the short-term responses of forests to weather extremes such as drought and heatwaves as well as about the long-term carbon sink behaviour of both forests and their vulnerability. Results based on machine learning approaches about the environmental and biological drivers of GHG fluxes at multiple scales will be presented along with their temporal contributions within and across years. Disentangling the role of climate vs. nitrogen (N) deposition for water-use efficiency of both tree species beech and spruce as well as linking tree to forest responses across scales will be discussed. Our experiences clearly demonstrate that using long-term, highly equipped EC sites as research platforms for additional research projects, nesting research programs within large-scale research infrastructure networks, and sharing data openly following FAIR principles, pays out, for one’s own curiosity, for career development of the next generation scientists, for policy advice and science at large!

PDF HTML阅读 XML下载 导出引用 引用提醒 博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O排放通量 DOI: 10.5846/stxb201610302213 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 新疆维吾尔自治区重点实验室专项基金项目（XJDX0909-2014-05）；新疆师范大学硕士研究生科技创新项目（XSY201602002） Emission fluxes of CO2, CH4, and N2O from artificial and natural reed wetlands in Bosten Lake, China Author: Affiliation: 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:为研究干旱区淡水湖泊人工、天然芦苇湿地土壤温室气体源汇强度及其影响因素，采用静态箱-气相色谱法，于2015年1月-12月对博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O通量进行全年观测。结果表明，人工芦苇湿地土壤CO2、CH4和N2O排放通量变化范围分别为：10.1-588.4mg m-2 h-1、2.9-82.4μg m-2 h-1和1.32-29.7μg m-2 h-1，天然芦苇湿地土壤CO2、CH4和N2O排放通量变化范围分别为10.3-469.6mg m-2 h-1、3.1-64.8μg m-2 h-1和1.9-14.3μg m-2 h-1。人工和天然芦苇湿地夏季土壤CO2排放通量均明显高于其他季节，而土壤CH4和N2O排放通量较大值多集中在春末夏初。全年观测期间，人工芦苇湿地土壤CO2、CH4和N2O排放通量高于天然芦苇湿地（P>0.05）；温度是影响人工、天然芦苇湿地土壤CO2和N2O排放通量的关键因素，近地面温度和5cm土壤温度与CO2和N2O排放通量呈现极显著的正相关关系（P<0.01）。土壤CH4排放通量是温度和水分二者共同影响的，由近地表温度、5cm土壤温度和土壤含水量共同拟合的方程可以分别解释人工、天然芦苇湿地土壤CH4排放通量的71%、74.5%；土壤有机碳、pH、盐分、NH4+-N、NO3--N也是人工、天然芦苇湿地土壤CO2、CH4和N2O排放通量的影响因素；人工和天然芦苇湿地土壤均是CO2、CH4和N2O的"源"。基于100年尺度，由3种温室气体计算全球增温潜势得出，人工芦苇湿地全球增温潜势大于天然芦苇湿地（15150.18kg/hm2 > 12484.21kg/hm2）。 Abstract:CO2, CH4, and N2O, have strong warming potentials and are considered to be the primary greenhouse gases in the atmosphere. Global warming caused by the increasing concentrations of atmospheric CO2, CH4, and N2O is one of the hotspots in global change field. Greenhouse gas (GHG) fluxes in reed wetlands are critical in evaluating the source/sink strength of GHG in arid area. We studied the dynamics of soil CO2, CH4, and N2O fluxes using static chamber-based on gas chromatography in two reed wetlands of the freshwater Bosten Lake, located in an arid area of Northwestern China. During a full year of monitoring, environmental variables (including soil moisture, soil temperature, air temperature, pH and salinity) were measured to determine the effects of abiotic factors on soil CO2, CH4, and N2O fluxes in artificial and natural reed wetlands. SPSS 19.0 for Windows was used to analyze the relationships between environmental factors and soil CO2, CH4, and N2O fluxes. The results showed that soil CO2, CH4, and N2O fluxes in the artificial reed wetland were 10.1-588.4mg m-2 h-1, 1.32-29.7μg m-2 h-1 and 3.1-64.8μg m-2 h-1, respectively, which was comparable with the values from the natural reed wetland. Higher soil CO2 emissions occurred in summer, whereas CH4 and N2O emissions mainly occurred in late spring and early summer. Temperature was the main factor controlling soil CO2 and N2O fluxes in both reed wetlands (P < 0.01). Soil CH4 emission flux was affected by both temperature and moisture. According to regression analysis, the combination of near-surface temperature, top 5cm soil temperature, and soil water content could explain 71% and 74.5% of soil CH4 flux in artificial and natural reed wetlands, respectively. Soil organic carbon, pH, salinity, NH4+-N, and NO3--N are also influencing factors of CO2, CH4, and N2O fluxes in artificial and natural reed wetlands. However, the differences in CO2, CH4, and N2O emissions from soils of artificial and natural reed wetlands were caused by differences in soil organic carbon, soluble nitrogen, and biomass. Based on the centennial scale, the soils of artificial and natural reed wetland were "sources" of GHG, and the global warming potential from artificial reed wetland was higher than that from natural reed wetland. 参考文献 相似文献 引证文献

We measured nitrous oxide (N2O) and carbon dioxide (CO2) fluxes from Gray Lowland soil (onion field) and Andosol soil (maize field) using the closed-chamber method and the concentration-gradient method based on Fick's law (gradient method). Measurements of gas concentration (at a depth of 0.05 m) and relative gas diffusion coefficients (D/D 0) (0–0.05 m depth) in the soil were carried out every week during the snow-free season (May–October) each year for 6 years in the Gray Lowland soil (1995–2000) and for 3 years in the Andosol soil (1998–2000). The seasonal pattern of N2O and CO2 fluxes using the chamber method was similar to those using the gradient method, and there were significant positive correlations between the fluxes using the chamber and gradient methods when extremely high N2O flux values were excluded (Smirnov–Grubbs’ outlier test, P < 0.01). There were no significant differences in N2O fluxes between the two methods, but CO2 flux using the chamber method was higher than that using the gradient method. As the gradient method could not measure the production, consumption and gas diffusion in the surface soil above the soil-air sampling tube (upper 0.05 m), differences in extremely high N2O and CO2 fluxes between the two methods resulted when the production and consumption of these gases were active in the soil above the installed location of the soil-air sampling tube. Measurements of gas concentration and D/D0 in the soil were required at every measurement during the investigation period because these values showed large seasonal variation. The measurement of CO2 flux was more influenced by plants than the N2O measurements. Therefore, it is necessary to consider the distance between the instruments (chambers and soil-air sampling tubes) and nearby plants. Our results suggest that the gradient method could lead to under or over estimation of CO2 flux and to extremely high N2O flux measurements. In contrast, the gradient method could be used for N2O flux measurement, excluding extremely high fluxes, and to understand seasonal patterns in CO2 flux. The gradient method is useful because it can estimate gas fluxes both in the soil and from soil to the atmosphere at the same time.

This study evaluates the impact of different forest management practices on soil greenhouse gas (GHG) fluxes in the R&amp;#228;nsk&amp;#228;l&amp;#228;nkorpi boreal drained forested peatland, in Southern Finland. The study site is part of the HoliSoils project (Holistic management practices, modelling, and monitoring for European forest soils; https://holisoils.eu/). The study is designed for a comparative analysis of non-harvested control, traditional clear-cut harvesting, and harvesting by continuous cover forestry (57% of basal area removed), carried out in spring 2021. The aim is to quantify mean differences in soil CO2, CH4, and N2O emissions and improve the annual budget estimates.Measurements of soil CO2, CH4, and N2O fluxes, soil temperature, moisture, water table depth, and air temperature were conducted post-harvest every two weeks during the growing season (May to November). Soil chemistry, understory vegetation, and microbial populations were also surveyed and evaluated for relations to observed spatial patterns of the GHG fluxes. Machine learning and Bayesian data assimilation techniques were employed (i) to identify relationships between GHG fluxes and environmental variables, and (ii) to model spatio-temporal dynamics.Clear-cutting (CUT) resulted in an immediate and sustained rise in the water table, with mean levels significantly higher than the control (CTR) and selection harvesting (COV) sites. In all CUT, COV, and CTR sites differences in mean values of soil CO2, CH4, and N2O fluxes were significant.Our findings underscore the significance of spatio-temporal variability in GHG fluxes across different management practices, highlight the management role in variation of dynamic environmental controls on CO2, CH4, and N2O fluxes, and reduce the knowledge gap on the effects of harvesting methods on GHG fluxes in boreal drained forested peatlands.

Effects of dredging wastewater input history and aquaculture type on greenhouse gas fluxes from mangrove sediments along the shorelines of the Jiulong River Estuary, China