scholarly journals Spatiotemporal Variations in Growing Season Exchanges of CO2, H2O, and Sensible Heat in Agricultural Fields of the Southern Great Plains

2007 ◽  
Vol 11 (17) ◽  
pp. 1-21 ◽  
Author(s):  
Marc L. Fischer ◽  
David P. Billesbach ◽  
Joseph A. Berry ◽  
William J. Riley ◽  
Margaret S. Torn
Keyword(s):  
Regression Model ◽  
Great Plains ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Growing Season ◽  
Temporal Variations ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Agricultural Fields ◽  
Southern Great Plains

Abstract Climate, vegetation cover, and management create finescale heterogeneity in unirrigated agricultural regions, with important but not well-quantified consequences for spatial and temporal variations in surface CO2, water, and heat fluxes. Eddy covariance fluxes were measured in seven agricultural fields—comprising winter wheat, pasture, and sorghum—in the U.S. Southern Great Plains (SGP) during the 2001–03 growing seasons. Land cover was the dominant source of variation in surface fluxes, with 50%–100% differences between fields planted in winter–spring versus fields planted in summer. Interannual variation was driven mainly by precipitation, which varied more than twofold between years. Peak aboveground biomass and growing season net ecosystem exchange (NEE) of CO2 increased in rough proportion to precipitation. Based on a partitioning of gross fluxes with a regression model, ecosystem respiration increased linearly with gross primary production, but with an offset that increased near the time of seed production. Because the regression model was designed for well-watered periods, it successfully retrieved NEE and ecosystem parameters during the peak growing season and identified periods of moisture limitation during the summer. In summary, the effects of crop type, land management, and water limitation on carbon, water, and energy fluxes were large. Capturing the controlling factors in landscape-scale models will be necessary to estimate the ecological feedbacks to climate and other environmental impacts associated with changing human needs for agricultural production of food, fiber, and energy.

scholarly journals The Great Plains Irrigation Experiment (GRAINEX)

2021 ◽  
pp. 1-66
Author(s):  
Eric Rappin ◽  
Rezaul Mahmood ◽  
Udaysankar Nair ◽  
Roger A. Pielke ◽  
William Brown ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Great Plains ◽  
Growing Season ◽  
Layer Growth ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Irrigated Agriculture ◽  
Strong Impact ◽  
Near Surface

AbstractExtensive expansion in irrigated agriculture has taken place over the last half century. Due to increased irrigation and resultant land use land cover change, the central United States has seen a decrease in temperature and changes in precipitation during the second half of 20th century. To investigate the impacts of widespread commencement of irrigation at the beginning of the growing season and continued irrigation throughout the summer on local and regional weather, the Great Plains Irrigation Experiment (GRAINEX) was conducted in the spring and summer of 2018 in southeastern Nebraska. GRAINEX consisted of two, 15-day intensive observation periods. Observational platforms from multiple agencies and universities were deployed to investigate the role of irrigation in surface moisture content, heat fluxes, diurnal boundary layer evolution, and local precipitation.This article provides an overview of the data collected and an analysis of the role of irrigation in land-atmosphere interactions on time scales from the seasonal to the diurnal. The analysis shows that a clear irrigation signal was apparent during the peak growing season in mid-July. This paper shows the strong impact of irrigation on surface fluxes, near-surface temperature and humidity, as well as boundary layer growth and decay.

scholarly journals Biases in regional carbon budgets from covariation of surface fluxes and weather in transport model inversions

2013 ◽  
Vol 13 (7) ◽  
pp. 19051-19083 ◽  
Author(s):  
I. N. Williams ◽  
W. J. Riley ◽  
M. S. Torn ◽  
S. C. Biraud ◽  
M. L. Fischer
Keyword(s):  
Boundary Layer ◽  
Time Scales ◽  
Great Plains ◽  
Seasonal Cycle ◽  
Transport Model ◽  
Surface Flux ◽  
Growing Season ◽  
Surface Fluxes ◽  
Southern Great Plains ◽  
Annual Variability

Abstract. Recent advances in transport model inversions could significantly reduce uncertainties in land carbon uptake through assimilation of high frequency CO2 concentration measurements. The impact of these measurements depends on the strength of covariation between surface fluxes and atmospheric transport and mixing at weekly and shorter time-scales, and on how well transport models represent this covariation. A stochastic boundary layer model was developed to quantify the effects of synoptic covariation on surface flux inversions at daily to season time-scales, and to compare covariation in transport model simulations to observations at the US Southern Great Plains Atmospheric Radiation Measurement Climate Research Facility. The most significant covariation of surface fluxes and transport occurred on weekly and longer time-scales, suggesting that surface flux inversions would benefit most from improved simulations of dynamics at the lower-frequency end of the synoptic spectrum. Biases in these rectifier effects contributed to surface flux biases of 13% of the seasonal cycle amplitude, estimated from differences between observations and a data assimilation system (CarbonTracker). Biases in simulated covariation of transport and surface fluxes resulted in overestimated boundary layer concentrations during the growing season over the Southern Great Plains, by up to 0.3 ppm CO2. Though small relative to the seasonal cycle, the strength of synoptic rectifier effects strongly varies on inter-annual time-scales, with some years having negligible and others having large vertical concentration gradients during the growing season, due only to differences in covariation of surface fluxes and transport. Inter-annual variability in vertical gradients due to synoptic rectifier effects is of similar magnitude to the inter-annual variability due to carbon sinks alone.

Rotational Cropping Systems to Reduce Cheat (Bromus secalinus) Densities

2006 ◽  
Vol 20 (2) ◽  
pp. 445-452 ◽  
Author(s):  
Jon C. Stone ◽  
Thomas F. Peeper ◽  
Amanda E. Stone
Keyword(s):  
Winter Wheat ◽  
Great Plains ◽  
Cropping Systems ◽  
Control Strategies ◽  
Growing Season ◽  
Grain Sorghum ◽  
Economic Returns ◽  
Southern Great Plains ◽  
Net Returns ◽  
Bromus Secalinus

In the Southern Great Plains, producers of hard red winter wheat seek sustainable methods for controlling cheat and improving economic returns. Experiments were conducted at two sites in north-central Oklahoma to determine the effect of cheat management programs, with various weed control strategies, on cheat densities and total net returns. The cheat management programs, initiated following harvest of winter wheat, included conventionally tilled, double-crop grain sorghum (Sorghum bicolorL.) followed by soybean (Glycine maxL.); and continuous winter wheat. Rotating out of winter wheat for one growing season increased yield of succedent wheat up to 32% and 42% at Billings and Ponca City, respectively. Dockage due to cheat in the succedent wheat was reduced up to 78% and 87% by rotating out of winter wheat for one growing season at Billings and Ponca City, respectively. Cheat management programs including a crop rotation with herbicides applied to the grain sorghum, except for an application of atrazine + metolachlor at Ponca City, improved total net returns over the nontreated continuous wheat option. Cheat panicles in the succedent wheat were reduced up to 87% by rotation out of winter wheat for one growing season.

scholarly journals Coupling between Large-Scale Atmospheric Processes and Mesoscale Land–Atmosphere Interactions in the U.S. Southern Great Plains during Summer. Part I: Case Studies

2004 ◽  
Vol 5 (6) ◽  
pp. 1223-1246 ◽  
Author(s):  
Christopher P. Weaver
Keyword(s):  
Great Plains ◽  
Large Scale ◽  
Deep Convection ◽  
Individual Case ◽  
Atmospheric Modeling ◽  
Surface Fluxes ◽  
Southern Great Plains ◽  
Atmospheric Processes ◽  
Mesoscale Processes

Abstract This paper is Part I of a two-part study that uses high-resolution Regional Atmospheric Modeling System (RAMS) simulations to investigate mesoscale land–atmosphere interactions in the summertime U.S. Southern Great Plains. The focus is on the atmospheric dynamics associated with mesoscale heterogeneity in the underlying surface fluxes: how shifts in meteorological regimes modulate these diurnal, mesoscale processes, and their overall impact at larger scales and over multiple diurnal cycles. Part I examines individual case study time periods drawn from the simulations that illustrate general points about the key land–atmosphere interactions. The main findings are as follows: The mesoscale processes are embedded within a synoptic-scale organization that controls the background meteorological regime at a given location. During the clear, dry days in the simulated months, heterogeneity in the surface fluxes forces strong, lower-tropospheric, mesoscale circulations that exhibit a characteristic dynamical life cycle over diurnal time scales. In general, the background large-scale flow does not affect the overall intensity of these coherent roll structures, though strong large-scale subsidence can sometimes dampen them. In addition, depending on the thermodynamic profile, the strong vertical motions associated with these circulations are sufficient to trigger shallow or even deep convection, with associated clouds and precipitation. Furthermore, surface heterogeneity sufficient to force such circulations can arise even without heterogeneity in preexisting land cover characteristics such as vegetation, for example, solely as a result of spatial variability in rainfall and other atmospheric processes. In Part II the mesoscale land–atmosphere interactions in these case study periods are placed in the larger context of the full, monthlong simulations.

scholarly journals The imprint of surface fluxes and transport on variations in total column carbon dioxide

2011 ◽  
Vol 8 (4) ◽  
pp. 7475-7524 ◽  
Author(s):  
G. Keppel-Aleks ◽  
P. O. Wennberg ◽  
R. A. Washenfelder ◽  
D. Wunch ◽  
T. Schneider ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Carbon Sink ◽  
Potential Temperature ◽  
Surface Flux ◽  
Growing Season ◽  
Temporal Variations ◽  
Surface Fluxes ◽  
Synoptic Scale ◽  
Meridional Gradient

Abstract. New observations of the vertically integrated CO2 mixing ratio, ⟨CO2⟩, from ground-based remote sensing show that variations in ⟨CO2⟩ are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large scale and local fluxes. Observations of both ⟨CO2⟩ and CO2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in ⟨CO2⟩ in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO2, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in ⟨CO2⟩ from covariations in ⟨CO2⟩ and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the ⟨CO2⟩ seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes as well as the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better reflect the observations. Our simulations suggest that boreal growing season NEE (between 45–65° N) is underestimated by ~40 % in CASA. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

scholarly journals The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

2015 ◽  
Vol 12 (23) ◽  
pp. 19781-19817
Author(s):  
A. E. Cassidy ◽  
A. Christen ◽  
G. H. R. Henry
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Arctic ◽  
Carbon Dioxide Fluxes ◽  
Tundra Ecosystem ◽  
Retrogressive Thaw Slump ◽  
Measurement Period

Abstract. Soil carbon stored in high-latitude permafrost landscapes is threatened by warming, and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, have increased in frequency and magnitude across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season the undisturbed tundra was a small net sink (NEE = −0.12 g C m−2 d−1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.39 g C m−2 d−1). Over the measurement period, the undisturbed tundra sequestered 3.84 g C m−2, while the disturbed tundra released 12.48 g C m−2. Before full leaf out in early July, the undisturbed tundra was a small source of CO2, but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.41 μmol m−2 s−1 and +0.50 μmol m−2 s−1, respectively) than those found in undisturbed tundra (+1.21 μmol m−2 s−1 and +1.00 μmol m−2 s−1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the growing season.

scholarly journals A model for urban biogenic CO<sub>2</sub> fluxes: Solar-Induced Fluorescence for Modeling Urban biogenic Fluxes (SMUrF v1)

2021 ◽  
Vol 14 (6) ◽  
pp. 3633-3661
Author(s):  
Dien Wu ◽  
John C. Lin ◽  
Henrique F. Duarte ◽  
Vineet Yadav ◽  
Nicholas C. Parazoo ◽  
...  
Keyword(s):  
Urban Areas ◽  
Fossil Fuel ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Co2 Fluxes ◽  
Biogenic Carbon ◽  
Urban Rural ◽  
Biogenic Fluxes

Abstract. When estimating fossil fuel carbon dioxide (FFCO2) emissions from observed CO2 concentrations, the accuracy can be hampered by biogenic carbon exchanges during the growing season, even for urban areas where strong fossil fuel emissions are found. While biogenic carbon fluxes have been studied extensively across natural vegetation types, biogenic carbon fluxes within an urban area have been challenging to quantify due to limited observations and differences between urban and rural regions. Here we developed a simple model representation, i.e., Solar-Induced Fluorescence (SIF) for Modeling Urban biogenic Fluxes (“SMUrF”), that estimates the gross primary production (GPP) and ecosystem respiration (Reco) over cities around the globe. Specifically, we leveraged space-based SIF, machine learning, eddy-covariance (EC) flux data, and ancillary remote-sensing-based products, and we developed algorithms to gap-fill fluxes for urban areas. Grid-level hourly mean net ecosystem exchange (NEE) fluxes are extracted from SMUrF and evaluated against (1) non-gap-filled measurements at 67 EC sites from FLUXNET during 2010–2014 (r>0.7 for most data-rich biomes), (2) independent observations at two urban vegetation and two crop EC sites over Indianapolis from August 2017 to December 2018 (r=0.75), and (3) an urban biospheric model based on fine-grained land cover classification in Los Angeles (r=0.83). Moreover, we compared SMUrF-based NEE with inventory-based FFCO2 emissions over 40 cities and addressed the urban–rural contrast in both the magnitude and timing of CO2 fluxes. To illustrate the application of SMUrF, we used it to interpret a few summertime satellite tracks over four cities and compared the urban–rural gradient in column CO2 (XCO2) anomalies due to NEE against XCO2 enhancements due to FFCO2 emissions. With rapid advances in space-based measurements and increased sampling of SIF and CO2 measurements over urban areas, SMUrF can be useful to inform the biogenic CO2 fluxes over highly vegetated regions during the growing season.

Characteristics of CO2, water vapor, and energy exchanges at a headwater wetland ecosystem of the Qinghai Lake

2019 ◽  
Vol 99 (3) ◽  
pp. 227-243
Author(s):  
Shengkui Cao ◽  
Guangchao Cao ◽  
Kelong Chen ◽  
Guangzhao Han ◽  
Ying Liu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Heat Fluxes ◽  
Qinghai Lake ◽  
Wetland Ecosystem ◽  
Monthly Average ◽  
Headwater Wetland ◽  
Heat Exchanges ◽  
Annual Scale

Ecosystem carbon dioxide (CO2), water vapor, and heat exchanges in alpine wetlands on the Qinghai–Tibetan Plateau are not comprehensively understood. Thus, we studied variability of net ecosystem CO2 exchange (NEE), ecosystem respiration (Re), gross primary production (GPP), evapotranspiration (ET), and heat fluxes over a headwater wetland ecosystem in the Qinghai Lake region. Results showed that the headwater wetland ecosystem was net CO2 absorption on the annual scale, in which monthly NEE, GPP, and Re in two consecutive years varied from −165.16 to 93 g CO2 m−2 mo−1, 6.66 to 384.45 g CO2 m−2 mo−1, and 6.9 to 232.02 g CO2 m−2 mo−1, respectively. The monthly ET from June to September was smaller than precipitation; these results reversed in the remaining months. Annual ET was 362.1 mm in 2015 and 324.96 mm in 2016. The net radiation (Rn), sensible heat (H), latent heat (LE), and ground heat (G) fluxes showed similar monthly patterns. Values of monthly average half-hour Rn, H, LE, and G at the daytime showed Rn > LE > H > G, and the time of the monthly half-hour G peak obviously lagged the Rn, H, and LE. Monthly average Bowen ratios were <1 from May to October, but it reversed in the rest of the months.

scholarly journals The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

2016 ◽  
Vol 13 (8) ◽  
pp. 2291-2303 ◽  
Author(s):  
Alison E. Cassidy ◽  
Andreas Christen ◽  
Gregory H. R. Henry
Keyword(s):  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Arctic ◽  
Carbon Dioxide Fluxes ◽  
Tundra Ecosystem ◽  
Retrogressive Thaw Slump ◽  
Measurement Period

Abstract. Soil carbon stored in high-latitude permafrost landscapes is threatened by warming and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, are present across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season, the undisturbed tundra was a small net sink (NEE  =  −0.1 g C m−2 d−1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE  =  +0.4 g C m−2 d−1). Over the measurement period, the undisturbed tundra sequestered 3.8 g C m−2, while the disturbed tundra released 12.5 g C m−2. Before full leaf-out in early July, the undisturbed tundra was a small source of CO2 but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure daytime fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.40 µmol m−2 s−1 and +0.55 µmol m−2 s−1, respectively) than those found in undisturbed tundra (+1.19 µmol m−2 s−1 and +1.04 µmol m−2 s−1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the majority of the growing season (late June and July).

scholarly journals Long-term drainage reduces CO<sub>2</sub> uptake and increases CO<sub>2</sub> emission on a Siberian floodplain due to shifts in vegetation community and soil thermal characteristics

2016 ◽  
Vol 13 (14) ◽  
pp. 4219-4235 ◽  
Author(s):  
Min Jung Kwon ◽  
Martin Heimann ◽  
Olaf Kolle ◽  
Kristina A. Luus ◽  
Edward A. G. Schuur ◽  
...  
Keyword(s):  
Primary Production ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Thermal Characteristics ◽  
Growing Season ◽  
Co2 Uptake ◽  
Vegetation Community ◽  
Uptake Rates ◽  
Soil Temperatures

Abstract. With increasing air temperatures and changing precipitation patterns forecast for the Arctic over the coming decades, the thawing of ice-rich permafrost is expected to increasingly alter hydrological conditions by creating mosaics of wetter and drier areas. The objective of this study is to investigate how 10 years of lowered water table depths of wet floodplain ecosystems would affect CO2 fluxes measured using a closed chamber system, focusing on the role of long-term changes in soil thermal characteristics and vegetation community structure. Drainage diminishes the heat capacity and thermal conductivity of organic soil, leading to warmer soil temperatures in shallow layers during the daytime and colder soil temperatures in deeper layers, resulting in a reduction in thaw depths. These soil temperature changes can intensify growing-season heterotrophic respiration by up to 95 %. With decreased autotrophic respiration due to reduced gross primary production under these dry conditions, the differences in ecosystem respiration rates in the present study were 25 %. We also found that a decade-long drainage installation significantly increased shrub abundance, while decreasing Eriophorum angustifolium abundance resulted in Carex sp. dominance. These two changes had opposing influences on gross primary production during the growing season: while the increased abundance of shrubs slightly increased gross primary production, the replacement of E. angustifolium by Carex sp.  significantly decreased it. With the effects of ecosystem respiration and gross primary production combined, net CO2 uptake rates varied between the two years, which can be attributed to Carex-dominated plots' sensitivity to climate. However, underlying processes showed consistent patterns: 10 years of drainage increased soil temperatures in shallow layers and replaced E. angustifolium by Carex sp., which increased CO2 emission and reduced CO2 uptake rates. During the non-growing season, drainage resulted in 4 times more CO2 emissions, with high sporadic fluxes; these fluxes were induced by soil temperatures, E. angustifolium abundance, and air pressure.

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