摘要 :
The National Ecological Observatory Network (NEON) is a multidecadal and continental-scale observatory with sites across the United States. Having entered its operational phase in 2018, NEON data products, software, and services b...
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The National Ecological Observatory Network (NEON) is a multidecadal and continental-scale observatory with sites across the United States. Having entered its operational phase in 2018, NEON data products, software, and services become available to facilitate research on the impacts of climate change, land-use change, and invasive species. An essential component of NEON are its 47 tower sites, where eddy-covariance (EC) sensors are operated to determine the surface-atmosphere exchange of momentum, heat, water, and CO2. EC tower networks such as AmeriFlux, the Integrated Carbon Observation System (ICOS), and NEON are vital for providing the distributed observations to address interactions at the soil-vegetation-atmosphere interface. NEON represents the largest single-provider EC network globally, with standardized observations and data processing explicitly designed for intersite comparability and analysis of feedbacks across multiple spatial and temporal scales. Furthermore, EC is tightly integrated with soil, meteorology, atmospheric chemistry, isotope, phenology, and rich contextual observations such as airborne remote sensing and in situ sampling bouts. Here, we present an overview of NEON's observational design, field operation, and data processing that yield community resources for the study of surface-atmosphere interactions. Near-real-time data products become available from the NEON Data Portal, and EC and meteorological data are ingested into AmeriFlux and FLUXNET globally harmonized data releases. Open-source software for reproducible, extensible, and portable data analysis includes the eddy4R family of R packages underlying the EC data product generation. These resources strive to integrate with existing infrastructures and networks, to suggest novel systemic solutions, and to synergize ongoing research efforts across science communities.
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摘要 :
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 N...
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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 CO<sub>2</sub>, 2.4–14.3?Hz for H<sub>2</sub>O, and 8.3–21.8?Hz for CO<sub>2</sub>, 1.4–19.9?Hz for H<sub>2</sub>O, 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 H<sub>2</sub>O and CO<sub>2</sub>. 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 H<sub>2</sub>O 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 H<sub>2</sub>O 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.
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摘要 :
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 N...
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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.
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摘要 :
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 N...
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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 4W 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 approximate to 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.
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The planning techniques and strategies for optimizing the urban wind and heat environment are important means for cities to adapt to climate change at the source. This study used Shenzhen, a sub-tropical megacity in southern China...
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The planning techniques and strategies for optimizing the urban wind and heat environment are important means for cities to adapt to climate change at the source. This study used Shenzhen, a sub-tropical megacity in southern China, as an example for evaluating the climate environment, heat island intensity, and urban form, and then for analyzing the relationships between them. The results revealed a high-quality climate area located southeast of Shenzhen that can provide a high wind speed and low temperature. Low-quality climate areas were located in the central and western regions and were less comfortable. The relationship between surface ventilation potential and urban form was analyzed using linear regression and the Pearson correlation coefficient, showing that there was a significant correlation between a surface urban heat island (SUHI) and building density (BD) as well as the sky view factor (SVF), and that there was also a correlation between the ventilation potential coefficient (VPC) and other factors, such as the surface’s roughness length (RL) and building height (BH). The results showed that ventilation capacity deteriorated as BH and RL increased. An environmentally sensitive thermal area was identified from the surface urban heat island intensity, which was always in a strong heat island (SHI) or sub-strong heat island (SSHI) year-round. It was recommended that seven level one corridors and nine level two corridors be formed. Additionally, thermal and wind environment optimization strategies and protective suggestions were proposed for the city’s overall development.
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Bacteria have been investigated as anti-tumor therapeutic agents for more than a century, since Coley first observed successful curing of a patient with inoperable cancer by injection of streptococcal organisms. Previous studies h...
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Bacteria have been investigated as anti-tumor therapeutic agents for more than a century, since Coley first observed successful curing of a patient with inoperable cancer by injection of streptococcal organisms. Previous studies have demonstrated that some obligate or facultative anaerobes can selectively accumulate and proliferate within tumors and suppress their growth. Developments in molecular biology as well as the complete genome sequencing of many bacterial species have increased the applicability of bacterial organisms for cancer treatment. In particular, the facultative anaerobe Salmonella Typhimurium has been widely studied and genetically engineered to improve its tumor-targeting ability as well as to reduce bacterial virulence. Moreover, the effectiveness of engineered attenuated S. Typhimurium strains employed as live delivery vectors of various antitumor therapeutic agents or combined with other therapies has been evaluated in a large number of animal experiments. The well-known S. Typhimurium mutant VNP20009 and its derivative strain TAPET-CD have even been applied in human clinical trials. However, Salmonella-mediated cancer therapies have not achieved the expected success, except in animal experiments. Many problems remain to be solved to exploit more promising strategies for combatting cancer with Salmonella bacteria. Here, we summarize the promising studies regarding cancer therapy mediated by Salmonella bacteria and highlight the main mechanisms of Salmonella anti-tumor activities.
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In the widely-used eddy-covariance (EC) technique, it is often assumed that the air storage term, i.e. the change of below-turbulence-sensor scalar abundance, is negligible or comprises a small part of net surface-atmosphere excha...
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In the widely-used eddy-covariance (EC) technique, it is often assumed that the air storage term, i.e. the change of below-turbulence-sensor scalar abundance, is negligible or comprises a small part of net surface-atmosphere exchange (NSAE). Previous studies have demonstrated that this assumption is often violated where non-turbulent processes prevail, and thus it is important to measure and calculate air storage in flux measurements. However, the implementation of air storage measurement and calculation is not ubiquitous as EC standard turbulent flux. In most cases, air storage is not a standard data product or even neglected in EC flux tower measurements. In other cases, air storage term is calculated simply using only the measurements at the tower top. This gap between the ideal initiative and actual implementation motivates us to derive and release one of the first community resources to facilitate the consistent measurement and calculation of EC air storage across sites. These resources include (i) the standardized air storage term measurement setup design at National Ecological Observatory Network (NEON) sites; (ii) the development and public release of the eddy4R.stor open-source air storage R-package; (iii) the derivation and public release of storage term data products, measured and calculated consistently across 47 NEON sites; and (iv) exploration the scientific usefulness of these resources through example use cases, specifically the exploration of the bias of the air storage term when different measurement level intensity used and exploration of the air storage term pattern. We expect the consistent air storage measurement and calculation can better serve the overall purpose of the EC technique to provide more reliable measurement of NSAE for the community. This can further benefit the community accurate depiction of the sub-daily to diurnal cycle of surface fluxes in doing carbon cycle flux partitioning, land modeling, and studying ecosystem response to weather extremes.
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Changes to global climate patterns have the potential to alter the structure of soil microbial communities which are key components of terrestrial ecosystems. High altitude ecosystems are both temperature and Nitrogen-limited and ...
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Changes to global climate patterns have the potential to alter the structure of soil microbial communities which are key components of terrestrial ecosystems. High altitude ecosystems are both temperature and Nitrogen-limited and the biota therein is sensitive to these conditions. Temperatures and nitrogen (N) depositions in the eastern Qinghai-Tibet Plateau are predicted to sharp rise by the end of this century. This study aimed to better understand the effects of warming and N addition treatments alone and in combination on an alpine meadow ecosystem near the timberline zone in the eastern region of the Qinghai-Tibet Plateau. The field experiment included replicated plots with an ambient treatment alone or with low N (5 g N m(-2) a(-1)), intermediate N (15 g N m(-2) a(-1)), and high N (30 g N m(-2) a(-1)) (Control, LN, MN, HN) and open top chambers warming treatment alone, or LN and HN additions (W, WLN, WHN) to study the interactive effects of the warming and N additions on the soil microbial community as determined by phospholipid fatty acids (PLFAs). Microbial communities and their allied soil and plant properties were examined after 3 years of the treatments. The strength of the relationship between the treatments and their direct and indirect effects on the microbial communities, soil and plant properties were determined using a structural equation model (SEqM). The results indicated that N addition significantly changed surface soil microbial communities, in particular, decreased the fungi: bacteria ratio (F: B) (p < 0.01). The warming differentially influenced some specific microbial biomarkers, such as fungal PLFAs which decreased, and actinobacterial PLFAs, which increased, under warming (p < 0.05). The combination of the warming and N addition showed significantly positive interactive effects (p < 0.001) on soil microorganisms (i.e. the biomass of general bacteria, Gram-positive bacteria, fungi and etc.) in these alpine soils. The SEqM results show the direct effects of the warming treatment on soil microorganisms were less than those from the N additions. Moreover, warming and N addition had stronger indirect, than direct, effects on the soil microbial community via induced changes in soil properties and plant community. The total effect of warming on the soil microbial community was stronger than that of the N additions. The results suggested interactive effects of the warming and N addition on soil microorganisms in an near timberline alpine ecosystem in the eastern Qinghai-Tibet Plateau. (C) 2016 Elsevier B.V. All rights reserved.
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Iron?(Fe) affects soil nitrogen?(N) cycling processes both in anoxic and oxic environments. The role of Fe in soil N transformations including nitrification, mineralization, and immobilization, is influenced by redox activity, whi...
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Iron?(Fe) affects soil nitrogen?(N) cycling processes both in anoxic and oxic environments. The role of Fe in soil N transformations including nitrification, mineralization, and immobilization, is influenced by redox activity, which is regulated by soil pH. The effect of Fe minerals, particularly oxides, on soil N transformation processes depends on soil pH, with Fe oxide often stimulating nitrification activity in the soil with low pH. We conducted lab incubations to investigate the effect of Fe oxide on N transformation rates in two subtropical agricultural soils with low pH (pH?5.1) and high pH (pH?7.8). <sup>15</sup>N-labeled ammonium and nitrate were used separately to determine N transformation rates combined with Fe oxide (ferrihydrite) addition. Iron oxide stimulated net nitrification in low-pH soil (pH?5.1), while the opposite occurred in high-pH soil (pH?7.8). Compared to the control, Fe oxide decreased microbial immobilization of inorganic N by 50?% in low-pH soil but increased it by 45?% in high-pH soil. A likely explanation for the effects at low pH is that Fe oxide increased NH<sub>3</sub>-N availability by stimulating N mineralization and inhibiting N immobilization. These results indicate that Fe oxide plays an important role in soil N transformation processes and the magnitude of the effect of Fe oxide is dependent significantly on soil pH.
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Iron?(Fe) affects soil nitrogen?(N) cycling processes both in anoxic and oxic environments. The role of Fe in soil N transformations including nitrification, mineralization, and immobilization, is influenced by redox activity, whi...
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Iron?(Fe) affects soil nitrogen?(N) cycling processes both in anoxic and oxic environments. The role of Fe in soil N transformations including nitrification, mineralization, and immobilization, is influenced by redox activity, which is regulated by soil pH. The effect of Fe minerals, particularly oxides, on soil N transformation processes depends on soil pH, with Fe oxide often stimulating nitrification activity in the soil with low pH. We conducted lab incubations to investigate the effect of Fe oxide on N transformation rates in two subtropical agricultural soils with low pH (pH?5.1) and high pH (pH?7.8). 15N-labeled ammonium and nitrate were used separately to determine N transformation rates combined with Fe oxide (ferrihydrite) addition. Iron oxide stimulated net nitrification in low-pH soil (pH?5.1), while the opposite occurred in high-pH soil (pH?7.8). Compared to the control, Fe oxide decreased microbial immobilization of inorganic N by 50?% in low-pH soil but increased it by 45?% in high-pH soil. A likely explanation for the effects at low pH is that Fe oxide increased NH3-N availability by stimulating N mineralization and inhibiting N immobilization. These results indicate that Fe oxide plays an important role in soil N transformation processes and the magnitude of the effect of Fe oxide is dependent significantly on soil pH.
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