scholarly journals Effects of cloudiness on carbon dioxide exchange over an irrigated maize cropland in northwestern China

2011 ◽  
Vol 8 (1) ◽  
pp. 1669-1691 ◽  
Author(s):  
B. C. Zhang ◽  
J. J. Cao ◽  
Y. F. Bai ◽  
S. J. Yang ◽  
L. Hu ◽  
...  
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Ecosystem Respiration ◽  
Meteorological Data ◽  
Exchange Process ◽  
Vapour Pressure Deficit ◽  
Northwestern China ◽  
Carbon Dioxide Exchange ◽  
Carbon Uptake ◽  
Carbon Exchange

Abstract. Clouds can strongly influence solar radiation and affects other microclimatic factors (such as air temperature and vapour pressure deficit), and those changed environmental conditions may exert strong effects on carbon exchange between terrestrial ecosystems and the atmosphere. In this study, we analyzed how canopy photosynthesis and ecosystem respiration respond to changes in cloudy conditions, based on two years of eddy-covariance and meteorological data from an irrigated maize cropland in Yingke oasis of northwestern China. The results showed that net carbon uptake was more negative under cloudy than under clear conditions, it indicates that net carbon uptake increased under cloudy days. The rate of ecosystem respiration (Re) decreased under cloudy conditions due to decreased air temperature. However, photosynthesis was suppressed by the decreasing air temperature and vapour pressure deficit (VPD) under cloudy skies. Thus, the enhancement of net carbon uptake under cloudy skies mainly contributed from increasing photosynthesis with diffuse radiation. Those results improve our understanding of the effects of cloud cover on carbon exchange process in maize (C4) cropland, and improve our understanding of the driver improving net carbon uptake under cloudy conditions.

Ecological responses of Stipa steppe in Inner Mongolia to experimentally increased temperature and precipitation. 4. Carbon exchange

2018 ◽  
Vol 40 (2) ◽  
pp. 159 ◽  
Author(s):  
Luomeng Chao ◽  
Zhiqiang Wan ◽  
Yulong Yan ◽  
Rui Gu ◽  
Yali Chen ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Air Temperature ◽  
Inner Mongolia ◽  
Ecosystem Respiration ◽  
Block Design ◽  
Net Ecosystem Exchange ◽  
Carbon Exchange ◽  
Ecosystem Productivity ◽  
Temperature And Precipitation ◽  
Gross Ecosystem Productivity

Aspects of carbon exchange were investigated in typical steppe east of Xilinhot city in Inner Mongolia. Four treatments with four replicates were imposed in a randomised block design: Control (C), warming (T), increased precipitation (P) and combined warming and increased precipitation (TP). Increased precipitation significantly increased both ecosystem respiration (ER) and soil respiration (SR) rates. Warming significantly reduced the ER rate but not the SR rate. The combination of increased precipitation and warming produced an intermediate response. The sensitivity of ER and SR to soil temperature and air temperature was assessed by calculating Q10 values: the increase in respiration for a 10°C increase in temperature. Q10 was lowest under T and TP, and highest under P. Both ER and SR all had significantly positive correlation with soil moisture. Increased precipitation increased net ecosystem exchange and gross ecosystem productivity, whereas warming reduced them. The combination of warming and increased precipitation had an intermediate effect. Both net ecosystem exchange and gross ecosystem productivity were positively related to soil moisture and negatively related to soil and air temperature. These findings suggest that predicted climate change in this region, involving both increased precipitation and warmer temperatures, will increase the net ecosystem exchange in the Stipa steppe meaning that the ecosystem will fix more carbon.

scholarly journals A psychrometric model to assess the biological decay of the SARS-CoV-2 virus in aerosols

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11024
Author(s):  
Clive B. Beggs ◽  
Eldad J. Avital
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Half Life ◽  
Analytical Study ◽  
Decay Constant ◽  
Meteorological Data ◽  
Environmental Parameters ◽  
Published Data ◽  
Reasonable Accuracy ◽  
The Impact

There is increasing evidence that the 2020 COVID-19 pandemic has been influenced by variations in air temperature and humidity. However, the impact that these environmental parameters have on survival of the SARS-CoV-2 virus has not been fully characterised. Therefore, an analytical study was undertaken using published data to develop a psychrometric model to assess the biological decay rate of the virus in aerosols. This revealed that it is possible to describe with reasonable accuracy (R2 = 0.718, p < 0.001) the biological decay constant for the SARS-CoV-2 virus using a regression model with enthalpy, vapour pressure and specific volume as predictors. Applying this to historical meteorological data from London, Paris and Milan over the pandemic period, produced results which indicate that the average half-life of the virus in aerosols outdoors was in the region 13–22 times longer in March 2020, when the outbreak was accelerating, than it was in August 2020 when epidemic in Europe was at its nadir. However, indoors, this variation is likely to be much less. As such, this suggests that changes in virus survivability due the variations in the psychrometric qualities of the air might influence the transmission of SARS-CoV-2.

scholarly journals Biophysical effects on the interannual variation in carbon dioxide exchange of an alpine meadow on the Tibetan Plateau

2017 ◽  
Vol 17 (8) ◽  
pp. 5119-5129 ◽  
Author(s):  
Lei Wang ◽  
Huizhi Liu ◽  
Jihua Sun ◽  
Yaping Shao
Keyword(s):  
Carbon Dioxide ◽  
Tibetan Plateau ◽  
Air Temperature ◽  
Interannual Variation ◽  
Alpine Meadow ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Seasonal Pattern ◽  
Carbon Dioxide Exchange ◽  
The Tibetan Plateau

Abstract. Eddy covariance measurements from 2012 to 2015 were used to investigate the interannual variation in carbon dioxide exchange and its control over an alpine meadow on the south-east margin of the Tibetan Plateau. The annual net ecosystem exchange (NEE) in the 4 years from 2012 to 2015 was −114.2, −158.5, −159.9 and −212.6 g C m−2 yr−1, and generally decreased with the mean annual air temperature (MAT). An exception occurred in 2014, which had the highest MAT. This was attributed to higher ecosystem respiration (RE) and similar gross primary production (GPP) in 2014 because the GPP increased with the MAT, but became saturated due to the limit in photosynthetic capacity. In the spring (March to May) of 2012, low air temperature (Ta) and drought events delayed grass germination and reduced GPP. In the late wet season (September to October) of 2012 and 2013, the low Ta in September and its negative effects on vegetation growth caused earlier grass senescence and significantly lower GPP. This indicates that the seasonal pattern of Ta has a substantial effect on the annual total GPP, which is consistent with results obtained using the homogeneity-of-slopes (HOS) model. The model results showed that the climatic seasonal variation explained 48.6 % of the GPP variability, while the percentages explained by climatic interannual variation and the ecosystem functional change were 9.7 and 10.6 %, respectively.

Stomatal characteristics and transpiration of three species of conifer seedlings planted on a high elevation south-facing clear-cut

1987 ◽  
Vol 17 (10) ◽  
pp. 1273-1282 ◽  
Author(s):  
N. J. Livingston ◽  
T. A. Black
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Soil Water Potential ◽  
Vapour Pressure Deficit ◽  
High Elevation ◽  
Boundary Line ◽  
Silver Fir ◽  
Clear Cut ◽  
Physiological Variables ◽  
Stomatal Responses

Douglas-fir (Pseudotsugamenziessi (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), and Pacific silver fir (Abiesamabalis (Doug.) Forbes) seedlings were planted in the spring as 1-0 container-grown plugs on a south-facing high elevation clear-cut located on Mount Arrowsmith, Vancouver Island, British Columbia, and their stomatal responses to environmental and physiological variables were determined over two successive growing seasons. The stomatal responses of all three species to changes in environmental variables and time did not differ over the 2 years nor were there differences in response between seedlings planted a year apart. A simple multiplicative boundary-line model that related seedling stomatal conductance (gs) to measurements of hourly average solar irradiance, air temperature, vapour pressure deficit, and average root zone soil water potential accounted for over 70% of the variability in gs. When the number of hours from sunrise was included as an independent variable, over 85% of the variability in gs could be explained. Daily seedlings transpiration rates on a projected leaf area basis were successfully estimated by summing the product of the calculated average gs and D/(RvT′) where D is the vapour pressure deficit, Rv is the gas constant for water vapour, and T′ is the absolute air temperature.

Stomatal Responses to Environmental Variables in Shade and Sun Grown Coffee Plants in Mexico

1985 ◽  
Vol 21 (3) ◽  
pp. 249-258 ◽  
Author(s):  
Luis Fanjul ◽  
R. Arreola-Rodriguez ◽  
M. P. Mendez-Castrejon
Keyword(s):  
Stomatal Conductance ◽  
Air Temperature ◽  
Environmental Conditions ◽  
Vapour Pressure ◽  
Environmental Variables ◽  
Vapour Pressure Deficit ◽  
Net Photosynthesis ◽  
Stomatal Movement ◽  
Stomatal Responses ◽  
Coffee Plants

SUMMARYThe influence of air temperature (T), vapour pressure deficit (vpd), irradiance (Q) and leaf water potential (ψ) on diurnal stomatal movement of coffee plants was examined under field and controlled environmental conditions. Leaves of plants grown under shade had larger stomatal conductance (g) values than plants grown in open sun. Stomatal responses to vpd under constant temperature conditions were very strong, indicating that ambient humidity could play a major role in controlling stomatal aperture. Changes in g as vpd increased probably contributed to observed reductions in the rate of net photosynthesis (Pn), though the effect of vpd on Pn was smaller.

scholarly journals Comparison of vapour pressure deficit patterns during cucumber cultivation in a traditional high PE tunnel greenhouse and a tunnel greenhouse equipped with a heat accumulator

2018 ◽  
Vol 16 (1) ◽  
pp. e0201 ◽  
Author(s):  
Paweł J. Konopacki ◽  
Waldemar Treder ◽  
Krzysztof Klamkowski
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Optimal Level ◽  
Water Vapour Pressure ◽  
Heat Accumulator ◽  
Climate Conditions ◽  
Excessive Heat ◽  
Protected Cultivation ◽  
The Difference

Plant productivity in protected cultivation is highly influenced by air temperature and humidity. The conditions relating to the moisture content of the air in protected plant cultivation are preferably defined by vapour pressure deficit (VPD), which describes the difference between the maximal and actual water vapour pressure (kPa). VPD is widely used as the parameter describing the climate conditions favourable for the development of fungal diseases and for highlighting conditions unfavourable for plant development. In protected cultivation, both the air temperature and the humidity are influenced by heating systems, and one such system is a heat accumulator, which may store the excessive heat produced during the day by converting the solar energy inside the plastic tunnel, and using it when plant heating is required. The tunnel equipped with a heat accumulator maintained an optimal level of humidity for a longer period, and significantly reduced the time of excessive air humidity. The longest time with an optimal VPD was recorded in August in a tunnel with an accumulator – 30.5% of total time vs. 22.3% of time for control tunnel. The highest difference of total time where the VPD was too low (below 0.2 kPa) was recorded in July – 12.4% of time in a tunnel with an accumulator vs. 39.1% of time for control tunnel. The highest difference of total time with an excessive VPD (over 1.4 kPa) was recorded in May – 12.1% of time in a tunnel with an accumulator vs. 17.9% of time for control tunnel. However, a situation beneficial for plant growth occurred every month during the investigated season.

scholarly journals Biophysical effects on the interannual variation in carbon dioxide exchange of an alpine meadow on the Tibetan Plateau

2016 ◽  
Author(s):  
Lei Wang ◽  
Huizhi Liu ◽  
Jihua Sun ◽  
Yaping Shao
Keyword(s):  
Carbon Dioxide ◽  
Tibetan Plateau ◽  
Air Temperature ◽  
Interannual Variation ◽  
Alpine Meadow ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Seasonal Pattern ◽  
Carbon Dioxide Exchange ◽  
The Tibetan Plateau

Abstract. Eddy covariance measurements from 2012 to 2015 were used to investigate the interannual variation in carbon dioxide exchange and its control over an alpine meadow on the southeast margin of the Tibetan Plateau. The annual net ecosystem exchange (NEE) from 2012 to 2015 was −114.2, −158.5, −159.9 and −212.6 g C m−2 yr−1 and generally decreased with the mean annual air temperature (MAT). An exception occurred in 2014, which had the highest MAT. This was attributed to higher ecosystem respiration (RE) and similar gross primary production (GPP) in 2014 because the GPP increased with MAT but became saturated due to the photosynthesis capacity limit. In the spring (March to May) of 2012, lower air temperature (Ta) and drought events delayed grass germination and reduced GPP. In the late wet season (September to October) of 2012 and 2013, the lower Ta in September and its negative effects on vegetation growth caused earlier grass senescence and significantly lower GPP. This indicates that the seasonal pattern of Ta greatly affected the annual total GPP, which is consistent with the result of the homogeneity-of-slopes model. The model shows that the climatic seasonal variation explained 48.6 % of the GPP variability, and the percentage of climatic interannual variation and the ecosystem functional change were 9.7 % and 10.6 %, respectively.

scholarly journals Thermal adaptation of net ecosystem exchange

2011 ◽  
Vol 8 (1) ◽  
pp. 1109-1136 ◽  
Author(s):  
W. Yuan ◽  
Y. Luo ◽  
S. Liang ◽  
G. Yu ◽  
S. Niu ◽  
...  
Keyword(s):  
Primary Production ◽  
Air Temperature ◽  
Ecosystem Respiration ◽  
Thermal Adaptation ◽  
Net Ecosystem Exchange ◽  
Carbon Uptake ◽  
Strongly Correlated ◽  
Response Curves ◽  
Mean Temperature ◽  
Source To Sink

Abstract. Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). In this study, we constructed temperature response curves of NEE against temperature using 380 site-years of eddy covariance data at 72 forest, grassland and shrubland ecosystems located at latitudes ranging from ~29° N to 64° N. The response curves were used to define two critical temperatures: transition temperature (Tb) at which ecosystem transferring from carbon source to sink and optimal temperature (To) at which carbon uptake is maximized. Tb was strongly correlated with annual mean air temperature. To was strongly correlated with mean temperature during the net carbon uptake period across the study ecosystems. Our results suggested that ecosystem CO2 flux switched from source to sink when air temperature reached annual mean temperature in spring and reached maximum uptake at mean temperature of the net carbon uptake period. Our results imply that the net ecosystem exchange of carbon adapt to the temperature across the geographical range due to intrinsic connections between vegetation primary production and ecosystem respiration.

scholarly journals Different Temperature and Humidity Responses to the Clear-Cut and the Gap in a Scots Pine Forest: A Study Case in Central Poland

2020 ◽  
Vol 3 (1) ◽  
pp. 74
Author(s):  
Longina Chojnacka-Ożga ◽  
Wojciech Ożga
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Heat Waves ◽  
Experimental Studies ◽  
Vapour Pressure Deficit ◽  
Summer Period ◽  
Clear Cut ◽  
Central Poland ◽  
The North ◽  
Thermal Diversity

In recent decades, relatively few experimental studies have been carried out in which the micrometeorological conditions have been studied over different small clearings plots of the forest. As these conditions can significantly affect many processes in the ecosystem, two questions arise: (1) whether and how the microclimatic conditions differ in the clear-cut and the gap, and (2) how heterogeneous the distribution of these conditions is on these plots. The aim of this study was to determine the spatial variation of air temperature on the clear-cut and gap as well as to compare the distribution of thermal and humidity conditions in both areas. The research was carried out in central Poland on a clear-cut with a width of 60 m and on a gap of an ellipsoid shape (40 × 70 m). The measurements were carried out in two series: spring–summer, during the period when the height of the sun during the day conditioned the inflow of direct solar radiation to any surface (May–August 2006), and autumn, when direct radiation was limited by neighbouring stands (October–November 2006). Average values of air temperature on the gap in the spring–summer period differed in individual parts of 2.2 °C, while on the clear-cut by 1.0 °C. In the autumn, thermal diversity on both research plots was similar (average 0.8 °C). The thermal diversity within the research areas was particularly marked in the case of extreme air temperature values. We found the modest spatial diversification of humidity parameters: vapour pressure, relative humidity, and humidity deficit. The particularly large diversification of relativity humidity and vapour pressure deficit occurred during the spring–summer period in the context of heat waves. The least beneficial thermal and humidity conditions for growing plants occurred in the north-eastern (NE) parts of the clear-cut and gap, which is why it is necessary to take particular note of these locations when undertaking silviculture.

scholarly journals Carbon dioxide exchange of a perennial bioenergy crop cultivation on a mineral soil

2016 ◽  
Vol 13 (4) ◽  
pp. 1255-1268 ◽  
Author(s):  
Saara E. Lind ◽  
Narasinha J. Shurpali ◽  
Olli Peltola ◽  
Ivan Mammarella ◽  
Niina Hyvönen ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ecosystem Respiration ◽  
Renewable Energy Sources ◽  
Mineral Soil ◽  
Vapour Pressure Deficit ◽  
Co2 Exchange ◽  
Carbon Dioxide Exchange ◽  
Bioenergy Crop ◽  
Comparison Site ◽  
Area Index

Abstract. One of the strategies to reduce carbon dioxide (CO2) emissions from the energy sector is to increase the use of renewable energy sources such as bioenergy crops. Bioenergy is not necessarily carbon neutral because of greenhouse gas (GHG) emissions during biomass production, field management and transportation. The present study focuses on the cultivation of reed canary grass (RCG, Phalaris arundinacea L.), a perennial bioenergy crop, on a mineral soil. To quantify the CO2 exchange of this RCG cultivation system, and to understand the key factors controlling its CO2 exchange, the net ecosystem CO2 exchange (NEE) was measured from July 2009 until the end of 2011 using the eddy covariance (EC) method. The RCG cultivation thrived well producing yields of 6200 and 6700 kg DW ha−1 in 2010 and 2011, respectively. Gross photosynthesis (GPP) was controlled mainly by radiation from June to September. Vapour pressure deficit (VPD), air temperature or soil moisture did not limit photosynthesis during the growing season. Total ecosystem respiration (TER) increased with soil temperature, green area index and GPP. Annual NEE was −262 and −256 g C m−2 in 2010 and 2011, respectively. Throughout the study period from July 2009 until the end of 2011, cumulative NEE was −575 g C m−2. Carbon balance and its regulatory factors were compared to the published results of a comparison site on drained organic soil cultivated with RCG in the same climate. On this mineral soil site, the RCG had higher capacity to take up CO2 from the atmosphere than on the comparison site.

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