Reducing CO2 Flux by Decreasing Tillage in Ohio: Overcoming Conjecture with Data

Predicting soybean evapotranspiration and crop water productivity for a tropical environment using the CSM-CROPGRO-Soybean model

During the summers of 1999 and 2000 measurments of component and ecosystem-level C02 fluxes were taken in seven cut blocks aged 0, 2, 3, 5, 6, 9 and 10years since harvest in the Aleza Lake Research Forest, near Prince George, British Columbia. A Bowen ratio energy balance (BREB) system was placed within a 5 to 6 year-old planted interior spruce (Picea glauca x Picea engelmanniz) clearcut to measure the ecosystem C02 flux during the 1999 and 2000 growing seasons. To substantiate the BREB measures of the ecosystem C02 flux a second method, called the component model, was established based on instantaneous measurements of component C02 fluxes (conifer, herbaceous plant, woody shrub and below ground) scaled up to the ecosystem-level. Both approaches indicated inter-annual variation in the growing season C02 fluxes. The 1999 growing season ecosystem C02 flux measurements estimated the clearcut to be a sink of -20 ~ 43 g C m~2 and -86 g C m~2 from 27 June to 3 September, using the BREB method and component model respectively. In contrast, in 2000 the growing season C02 flux during the same time period was a source of 43 g C m~2 (BREB method) and 66 ~44 g C m~2 (component model) during the same period. In 2000, an additional 50 days of measurement, from 24 May to 20 September, indicated an even larger source of C02 totaling 143 ~57 and 103 g C m~2 using the BREB method and component model, respectively. However, regardless of the approach used, both years would have been sources of C02 if additional measures were taken for the entire year. The component fluxes were dominated by the C02 source from below ground (338 and 466 g C m~2 in 1999 and 2000, respectively) and the C02 sink provided by the deciduous plants (-382 and -365 g C m~2 in 1999 and 2000 respectively). The conifer photosynthetic C02 uptake for the 5 to 6 year-old clearcut was meager in comparison (-47 and -57 g C m~2 in 1999 and 2000, respectively). During the 2000 growing season, the below ground C02 flux and above ground biomass was measured in 7 cut blocks aged 0, 2, 3, 5, 6, 9 and 10 years and one mature stand. All sites were in the SBS wkl 08 or 07 except the 0 and 9 year-old sites that were of the sub series 01. The growing season below ground C02 flux was similar for all cut blocks, including the mature forest. Furthermore, there was little change in above ground biomass carbon uptake between the different aged cut blocks. Hence, when biomass was incorporated with the below ground C02 fluxes all cut blocks were sources for C02\u2022 Therefore, cut blocks within the Aleza Lake region (SBS wk1 07 or 08) are sources of C02 for at least 10 years after harvest because the conifer component of the C02 flux is incapable of surmounting the loss of C02 from below ground.

<p>Evapotranspiration is an important parameter for grassland ecosystems because the (actual) evapotranspiration explains the exchange of water and energy between soil, land surface and atmosphere. Understanding the effects of changing grassland yields on evapotranspiration rates is essential for the assessment of the water- and plant water balance of grassland sites under climate change. However, evapotranspiration is difficult to measure, and the suitability of the various methods strongly depends on the time and spatial scale considered. Thus, the aim of this work is to compare different measurements of actual evapotranspiration (ETa) at a managed alpine grassland site. The study area is located in the northern alps of Austria, at the Agricultural Research and Education Centre Raumberg-Gumpenstein (Styria). Here, the ETa data of a high resolution weighable lysimeters, are compared with ETa data measured by a scintillometer system BLS900 (Scintec, Germany). The system measures sensible heat flux integrated along the near-infrared beam of 880 nm, length of 356 m and height of 6.3 m above grassy surface. The ETa is calculated as a residual from the energy balance equation. Another independent source of ETa data is the Bowen ratio energy balance system (BREB), which is placed roughly in the middle of the scintillometer path and adjacently (few meters) to the lysimeter.</p><p>During the observation period (vegetation period 2018; March-November), ETa calculated from the weighable lysimeter was 573 mm in total and showed the highest absolute value compared to the other measurements. The calculated ETa from the BREB system is 505 mm (including condensation) and 526 mm (excluding condensation).</p><p>At the beginning of the vegetation growth, the scintillometer system measured lower values of ETa than the lysimeter, but higher values than the BREB system. Contrary, at the end of May, the lysimeter ETa showed the lowest values compared to the other two systems. This can be related to the fact that the grass on the lysimeter was cut three times per year, whereas the management of other areas on the experimental site was different. The same effects were observed at the second and third cut, always with the fact that the scintillometer system showed higher values than the BREB system. After two weeks of the first and second cut, the vegetation on the lysimeters was established faster than on the surrounding grassland. As a consequence, the lysimeter ETa showed again the highest values. Only after the third cut at the end of September, the vegetation was slowly growing and the scintillometer as well the BREB system showed higher ETa values till the end of the observation month in November. These results suggest that the evapotranspiration rates are strongly dependent on the management of the grassland, which needs to be considered in the selection and design of evapotranspiration measurements.</p>

The large area occupied by temperate grassland ecosystems makes it important to determine their strength as a carbon sink. The Bowen ratio/energy balance (BREB) technique was used to determine CO2 fluxes over a moderately grazed mixed-grass prairie at Mandan, North Dakota, USA, over a 6-year period from 1996 to 2001. Above-ground biomass and leaf area index (LAI) were measured about every 21 days throughout the growing period. Root biomass was determined to 1.1 m depth in mid-July each year. Peak above-ground biomass typically occurred between mid-July to early August and ranged from 782 kg/ha in 1998 to 2173 kg/ha in 1999. Maximum LAI ranged from 0.4 in 1998 to 0.9 in 1999. Root biomass ranged from 11.8 Mg/ha in 1997 to 17.4 Mg/ha in 1996. Maximum daily CO2 fluxes generally coincided with periods of maximum LAI and above-ground green biomass. The average time period for CO2 uptake was 5 May to 3 October. Annual CO2 fluxes ranged from a low of 13 g CO2/m2 in 1998 to a high of 247 g CO2/m2 in 2001, nearly a 20-fold difference, and averaged 108 g CO2/m2. The cumulative annual flux over all 6 years was 646 g CO2/m2 or 176 g CO2-C/m2. These results indicate that the strength of the carbon sink for this moderately grazed prairie site is about 30 g CO2-C/m2/yr, which is quite small, but considering that the site was grazed and still remains a sink for carbon, it is significant.

We report an open-path and anti-pollution multi-pass cell based tunable diode laser absorption spectroscopy (TDLAS) sensor, which was designed for online measurement of atmospheric H2O and CO2 fluxes. It is mainly composed of two plano-convex mirrors coated on a convex surface, which makes it different from traditional multi-pass cells. This design does not allow a direct contact between the coating layer of the lens and air, thereby realizing the anti-pollution effect of the coating layer. Two DFB lasers operating at 1392 nm and 2004 nm were employed to target H2O and CO2 absorption lines, respectively. Allan analysis of variance indicated that detection limits of H2O and CO2 were 5.98 ppm and 0.68 ppm, respectively, at an average time of 0.1 s. The sensor performance was demonstrated by measuring CO2 and H2O flux emissions at Jiangdu Agricultural Monitoring Station in Jiangsu Province. The results were compared with those obtained using the commercial instrument LI-7500, which is based on non-dispersive infrared technology. The developed gas analysis instrument exhibited good consistency with commercial instruments, and its accuracy was comparable; thus, it has strong application prospects for flux measurements in any ecosystem.

In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one‐dimensional gas flow through a soil of known permeability. Using the advective‐diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 × 10−2 to 1.23 × 102 μm2) were used. The CO2 flux values were varied from 0.1 kg m−2 d−1 up to 22 kg m−2 d−1. On the basis of these results, a new empirical equation for calculating very accurate soil CO2 flux from dynamic concentration and soil permeability values was proposed. As highlighted by the experimental data, the influence of soil permeability on CO2 flux measurements depends on various factors, of which the flow rate of the suction pump is the most important. Setting low values for the pumping flux (0.4–0.8 L min−1), the mean error due to soil permeability was lower than 5%. Finally, the method was tested by measuring the CO2 flux in a grid of 48 sampling sites on Vulcano (Aeolian Islands, Italy), and the global error, affecting the CO2 flux measurements in a real application, was evaluated.

The paper presents an analysis, performed at the Royal Netherlands Meteorological Institute (KNMI), of data obtained at a research platform 9 km off the Dutch coast within the framework of the air’sea gas exchange program ASGAMAGE†. The air’sea transfer velocity of CO2 was determined directly, that is, by observing CO2 fluxes and air’sea concentration differences simultaneously. CO2 fluxes were determined by means of the eddy correlation technique. Special care was taken to avoid the effects water vapour on the CO2 flux measurements. The air and water near the air’sea interface were treated as well-mixed with respect to CO2. The combination of flux and concentration data allowed the computation of the transfer velocity for CO2 without recourse to other gases. Results for two observation periods, one with downward CO2fluxes (May) and one with upward CO2 fluxes (October), are consistent. A relation with UN,10, the wind speed adjusted to a height of 10 m and neutral stratification, was determined for the pooled data from the two experimental phases. The relation found was: k660 = 0.54U2N,102 cm h-1, with k660 the CO2 transfer velocity normalized to salt water (35‰) at a temperature of 20 °C, and UN,10 in m s-1. The 95% confidence interval of the coefficient extends from 0.46 to 0.63. No relations with other geophysical parameters could be found from the present data set.ASGAMAGE is a contraction of ASGASEX (for Air Sea Gas Exchange), an earlier experiment in this field, and MAGE, the Marine Aerosol and Gas Exchange activity of the International Global Atmospheric Chemistry program (IGAC).

The daytime variation in CO2 flux between the intertidal sediment and the atmosphere was great and impacted by environmental elements. This paper analyzed the daytime variation in CO2 flux between the intertidal sediment and the atmosphere and concluded its different rules during the ebb tide and flood tide. During the ebb tide, the CO2 flux rose as the tide ebbed and its rate of change was different when the redox potential changed (0.13umol m-2 s-1 per 100 cm height of the tide at Eh<=300mv, 0.15umol m-2 s-1 per 100 cm height of the tide at 300mv<Eh<500mv and 0.07umol m-2 s-1 per 100 cm height of the tide at Eh>=500mv). During the flood tide, the CO2 flux maintained the largest of the day and almost unchanged with the increase of water level. The average CO2 flux in the flood tide increased with the increase of the redox potential at Eh<=300mv and 300mv<Eh<500mv, but their linear regressions between the average CO2 flux and the redox potential were different. Compared with the average CO2 flux at Eh<=300mv and 300mv<Eh<500mv, the average CO2 flux was no longer related to the redox potential but related to temperature at Eh>=500mv. According to these rules, the daytime CO2 flux can be calculated based on limited measurements well and truly. The fitting straight line equation between the estimated and measured CO2 flux was y= 0.9353x+0.0872(R2 = 0.75, P <0.01).

Understanding the field‐scale variability of CO 2 fluxes in space and time under different land‐use conditions is important for designing efficient sampling schemes for monitoring C loss from soil. The objectives of this study were to characterize the variability structure of CO 2 fluxes and its change throughout a year, evaluate the temporal stability of spatial CO 2 flux patterns, and quantify relationships with biotic and abiotic factors in crop and grass systems. In an 80‐ by 60‐m field divided into grass and crop systems, CO 2 fluxes were measured with a photo‐acoustic analyzer at 60 locations 22 times during a year. Soil respiration was high when it was warm and wet and low under cool and wet conditions. Measurements of CO 2 flux were spatially and temporally dependent for a longer distance and time in the grass system than in the crop system. Spatial patterns of soil respiration were temporally stable, and the larger the average spatial CO 2 flux, the more obvious was the temporal stability. The variation of soil respiration was more pronounced in time than in space during the study period. At each location, soil temperature was the major factor controlling the temporal variability of CO 2 flux; however, soil temperature did not explain the spatial CO 2 flux pattern. Land use impacted the spatial and temporal variability dynamics of CO 2 flux. These dynamics should be taken into account for experimental design, the detection of spatial and temporal associations with other variables, and C loss prediction.

An integrated field-laboratory program evaluated the use of radon and CO2 flux measurements to constrain source and timescale of CO2 fluxes in environments proximate to CO2 storage reservoirs. By understanding the type and depth of the gas source, the integrity of a CO2 storage reservoir can be assessed and monitored. The concept is based on correlations of radon and CO2 fluxes observed in volcanic systems. This fundamental research is designed to advance the science of Monitoring, Verification, and Accounting (MVA) and to address the Carbon Storage Program goal of developing and validating technologies to ensure 99 percent storage performance. Graduate and undergraduate students conducted the research under the guidance of the Principal Investigators; in doing so they were provided with training opportunities in skills required for implementing and deploying CCS technologies. Although a final method or “tool” was not developed, significant progress was made. The field program identified issues with measuring radon in environments rich in CO2. Laboratory experiments determined a correction factor to apply to radon measurements made in CO2-bearing environments. The field program also identified issues with radon and CO2-flux measurements in soil gases at a natural CO2 analog. A systematic survey of radon and CO2 flux in soil gases at the LaBarge CO2 Field in Southwest Wyoming indicates that measurements of 222Rn (radon), 220Rn (thoron), and CO2 flux may not be a robust method for monitoring the integrity of a CO2 storage reservoir. The field program was also not able to correlate radon and CO2 flux in the CO2-charged springs of the Thermopolis hydrothermal system. However, this part of the program helped to motivate the aforementioned laboratory experiments that determined correction factors for measuring radon in CO2-rich environments. A graduate student earned a Master of Science degree for this part of the field program; she is currently employed with a geologic consulting company. Measurement of radon in springs has improved significantly since the field program first began; however, in situ measurement of 222Rn and particularly 220Rn in springs is problematic. Future refinements include simultaneous salinity measurements and systematic corrections, or adjustments to the partition coefficient as needed for more accurate radon concentration determination. A graduate student earned a Master of Science degree for this part of the field program; he is currently employed with a geologic consulting company. Both graduate students are poised to begin work in a CCS technology area. Laboratory experiments evaluated important process-level fundamentals that effect measurements of radon and CO2. Laboratory tests established that fine-grained source minerals yield higher radon emissivity compared to coarser-sized source minerals; subtleties in the dataset suggest that grain size alone is not fully representative of all the processes controlling the ability of radon to escape its mineral host. Emissivity for both 222Rn and 220Rn increases linearly with temperature due to reaction of rocks with water, consistent with faster diffusion and enhanced mineral dissolution at higher temperatures. The presence of CO2 changes the relative importance of the factors that control release of radon. Emissivity for both 222Rn and 220Rn in CO2-bearing experiments is greater at all temperatures compared to the experiments without CO2, but emissivity does not increase as a simple function of temperature. Governing processes may include a balance between enhanced dissolution versus carbonate mineral formation in CO2-rich waters.

Measurements of soil CO2 flux in the absence of living plants can be used to evaluate the effectiveness of soil management practices for C sequestration, but field CO2 flux is spatially variable and may be affected by soil compaction and the percentage of total pore space filled with water (%WFPS). The objectives of our study were: (i) to evaluate the effect of wheel traffic compaction on CO2 flux at two landscape positions with differing soil properties; and (ii) to examine the relationship of CO2 flux and %WFPS under field conditions and a wide range of soil porosities. Carbon dioxide flux was measured near Ames, IA, in a no-till system without living plants using the closed chamber method on nine cylinders inserted into the soil at each measurement site and evenly spaced across three rows, an untracked interrow, and a tracked interrow. Flux, volumetric water contents, and soil temperature were measured on 12 or 13 d between day of the year (DOY) 164 and 284 in 2001, 2004, and 2005. Bulk density, soil organic C concentration, and soil texture were determined after DOY 284. On most days, CO2 flux was less in the tracked interrow than in the row or untracked interrow positions. In all 3 yr, the cumulative flux of the tracked position was significantly less than one or both of the other positions. Landscape position did not affect the response of CO2 flux to traffic. Percentage water-filled pore space was not a good predictor of surface CO2 flux in the field. The effect of wheel traffic compaction on CO2 flux should be considered when soil CO2 flux is used to compare management practices.

Adopting soil and crop management practices that conserve or enhance soil structure is critical for supporting the sustainable adaptation of agriculture to climate change, as it should help maintain agricultural production in the face of increasing drought or water excess without impairing environmental quality. In this paper, we evaluate the evidence for this assertion by synthesizing the results of 34 published meta-analyses of the effects of such practices on soil physical and hydraulic properties relevant for climate change adaptation in European agriculture. We also review an additional 127 meta-analyses that investigated synergies and trade-offs or help to explain the effects of soil and crop management in terms of the underlying processes and mechanisms. Finally, we identify how responses to alternative soil-crop management systems vary under contrasting agro-environmental conditions across Europe. This information may help practitioners and policymakers to draw context-specific conclusions concerning the efficacy of management practices as climate adaptation tools. Our synthesis demonstrates that organic soil amendments and the adoption of practices that maintain “continuous living cover” result in significant benefits for the water regulation function of soils, mostly arising from the additional carbon inputs to soil and the stimulation of biological processes. These effects are clearly related to improved soil aggregation and enhanced bio-porosity, both of which reduce surface runoff and increase infiltration. One potentially negative consequence of these systems is a reduction in soil water storage and groundwater recharge, which may be problematic in dry climates. Some important synergies are reductions in nitrate leaching to groundwater and greenhouse gas emissions for non-leguminous cover crop systems. The benefits of reducing tillage intensity appear much less clear-cut. Increases in soil bulk density due to traffic compaction are commonly reported. However, biological activity is enhanced under reduced tillage intensity, which should improve soil structure, infiltration capacity, and reduce surface runoff and the losses of agro-chemicals to surface water. However, the evidence for these beneficial effects is inconclusive, while significant trade-offs include yield penalties and increases in greenhouse gas emissions and the risks of leaching of pesticides and nitrate.

Characteristics of atmospheric CO2 fluxes and the estimation of their potential sources around Boseong Standard Weather Observatory (BSWO)

Evapotranspiration model for semi-arid shrub-lands tested against data from SE Spain

We present the carbon dioxide and water flux data along with associated meteorological data collected by the U.S. Department of Agriculture Agricultural Research Service, Southwest Watershed Research Center, on the Walnut Gulch Experimental Watershed from 1997 through 2006. Measurements were collected from a shrub and grass community using the Bowen ratio energy balance systems and were presented in 20‐min time steps. Meteorological and Bowen ratio data were imported into spreadsheets for quality control and calculations of carbon dioxide and water fluxes. The data are available at http://www.tucson.ars.ag.gov/dap/.