Free-air Carbon Dioxide Enrichment Experiment Research Articles

Field experimental data for crop modeling of wheat growth response to nitrogen fertilizer, elevated CO2, water stress, and high temperature

Field experimental data of five experiments covering a wide range of growing conditions are assembled for wheat growth and cropping systems modeling. The data include an experiment on interactive effects of elevated CO2 by water and elevated CO2 by nitrogen fertilizer application from a Free-Air Carbon Dioxide Enrichment experiment (FACE) at Arizona in USA; a nitrogen rate fertilizer experiment from three locations and two years in The Netherlands; water deficit experiments at Lincoln in New Zealand and at Cunderdin in Australia; and a temperature sensitivity experiment at Obregon in Mexico. The data consist of 65 experimental treatments with more than 1000 detailed observations, with time series of development and growth, soil water and soil nitrogen dynamics, yield and yield components, daily weather, soil characteristics, and cultivar descriptions. These data have been used in various previous agronomic and crop modeling studies. Assembled data are quality checked and supplied in Agricultural Model Inter-comparison and Improvement (AgMIP) format. Data access via DOI 10.7910/DVN/V4P6PU.

Integrating regional climatology, ecology, and agronomy for impact analysis and climate change adaptation of German agriculture: An introduction to the LandCaRe2020 project

One of the most decisive natural framework conditions of agriculture – the regional climate – is in transition. This requires considering climate change and climate change impact for decision making. Although this knowledge is uncertain and depends on future green-house gas emission, it is rapidly expanding and improving. Therefore, it is important to create flexible systems with adaptable data bases and analytical tools to integrate knowledge of future climate change in agronomy for impact studies and adaptation planning. The joint project LandCaRe (Land, Climate, and Resources) 2020 aimed at developing a conceptual framework and prototype of a model-based decision support system (DSS) based on improved process knowledge and stakeholder communication. The final product, the LandCaRe DSS should combine grid-based information on regional climate and land surface, robust climate impact models and socio-economic boundary conditions to develop spatially explicit climate impact scenarios. Emphasis was put on the integration of different knowledge from science and practice. Climate projections had to be adapted to the needs of impact modelling of agricultural and ecological processes at regional and farm scale. Impact modelling included new process knowledge, especially related to the CO2 fertilisation effect on crop rotations. A new Free Air Carbon Dioxide Enrichment Experiment (FACE) on the C4 plant maize was conducted during the project. A new agro-ecosystem model was developed which integrates soil–plant–atmosphere exchange and plant production to predict crop yield as well as water, carbon and nitrogen fluxes. Stakeholders included representatives of agricultural and environmental administrations, managers of agro-enterprises and large farms as well as organisations for regional planning and nature conservation. Their central common interests were future land use, water availability and management. Stakeholders from agriculture requested not only to assess potential impacts of regional climate change on yield but also to interpret climate impact on farm economy. This required the design of a farm-economy module linking effects of management and adaptation on crop yield with scenarios of costs and prices. Here an introduction to the project, components of the DSS and its further perspectives are presented.

Understand distribution of carbon dioxide to interpret crop growth data: Australian grains free-air carbon dioxide enrichment experiment

Carbon dioxide (CO2) is the most important greenhouse gas, predicted to increase globally from currently 386 to 550 μmol mol–1 by 2050 and cause significant stimulation to plant growth. Consequently, in 2007 and 2008, Australian grains free-air carbon dioxide enrichment (AGFACE) facilities were established at Horsham (36°45′07″S lat., 142°06′52″E long., 127 m elevation) and Walpeup (35°07′20″S lat., 142°00′18″E long., 103 m elevation) in Victoria, Australia to investigate the effects of elevated CO2, water supply and nitrogen fertiliser on crop growth. Understanding the distribution patterns of CO2 inside AGFACE rings is crucial for the interpretation of the crop growth data. In the AGFACE system, the engineering performance goal was set as having at least 80% of the ring area with a CO2 concentration [CO2] at or above 90% of the target concentration at the ring-centre for 80% of the time. The [CO2] was highly variable near the ring-edge where CO2 is emitted and declined non-linearly with the distance downwind and wind speeds. Larger rings maintained the target [CO2] of 550 μmol mol–1 at the ring-centres better than the smaller rings. The spatial variation of [CO2] depended on ring size and the gap between fumigation and canopy heights but not on wind speeds. The variations in the inner 80% of the rings were found to be higher in smaller rings, implying that the larger rings had more areas of relatively uniform [CO2] to conduct experiments.

Measurement of carbon dioxide fluxes in a free-air carbon dioxide enrichment experiment using the closed flux chamber technique

Abstract Carbon dioxide (CO2) fluxes, composing net ecosystem exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) were measured in a temperate heathland exposed to elevated CO2 by the FACE (free-air carbon enrichment) technique, raising the atmospheric CO2 concentration from c. 380 μmol mol−1 to 510 μmol mol−1. All CO2 fluxes were measured by the static chamber methodology. Although the FACE technique enriches the atmosphere with CO2 to a fixed level, the above ground CO2 concentrations may nevertheless locally vary strongly (from about ambient to ∼1000 μmol mol−1). Deployment of static chambers to FACE experiments should therefore be performed with great care in order to ensure reproducible conditions with respect to chamber headspace CO2 concentration. We demonstrate that that the fluxes measured by closed chambers relate linearly to the initial headspace CO2 concentration. When changing the initial headspace CO2 concentration from 380 to 510 μmol mol−1 the net CO2 assimilation expressed by NEE increased instantaneously 1.51 times in control plots and 1.71 times in FACE plots. By contrast, ER in control plots decreased, being 0.87 times that measured at the low CO2 concentration, and the flux also decreased in FACE plots, to 0.79 times that at low concentration. Similar SR in control plots was decreased 0.94 times in control plots and 0.88 times in FACE plots. We found that a useful method to achieve stable and reproducible chamber headspace and soil CO2 concentration prior to commencement of flux measurements was to turn off the FACE system at least 10 min in advance. Within 10 min a new equilibrium was established between the soil and atmosphere, apparently due to CO2 degassing from the top soil. The observed increase in SR in response to increased CO2 persisted for up to 18 h during which measurements should be performed. Soil CO2 concentrations were increased by up to 500 μmol mol−1 by the FACE treatment, substantially more than the 130 μmol mol−1 enrichment achieved in the atmosphere suggesting that the increased SR flux was caused by increased belowground respiration.

Response of saprotrophic microfungi degrading the fulvic fraction of soil organic matter to different N fertilization intensities, different plant species cover and elevated atmospheric CO2 concentration.

The response of the cenosis composition of soil saprotrophic microfungi able to utilize the fulvic fraction of soil organic matter to increased concentration of atmospheric carbon dioxide, plant species cover quality and different levels of nitrogen fertilization was determined under field conditions in a free-air carbon dioxide enrichment experiment. Twenty-nine species of microfungi were isolated from the tested soil. The effects of CO2 enrichment and plant species cover were not significant. Nitrogen fertilization was identified as the only significant factor inducing changes in the abundance of soil microorganisms. This was reflected in a relatively low value of quantitative Sørensen similarity index on comparing fertilized and unfertilized treatments and in 2-way ANOVA of total CFU counts. Some differences were observed in species diversity between the two variants of all treatments. No association between microfungi and the factors under study was found by using the Monte Carlo Permutation test in redundancy analysis.

Impacts of fine root turnover on forest NPP and soil C sequestration potential.

Estimates of forest net primary production (NPP) demand accurate estimates of root production and turnover. We assessed root turnover with the use of an isotope tracer in two forest free-air carbon dioxide enrichment experiments. Growth at elevated carbon dioxide did not accelerate root turnover in either the pine or the hardwood forest. Turnover of fine root carbon varied from 1.2 to 9 years, depending on root diameter and dominant tree species. These long turnover times suggest that root production and turnover in forests have been overestimated and that sequestration of anthropogenic atmospheric carbon in forest soils may be lower than currently estimated.