Does elevated atmospheric CO2 allow for sufficient wheat grain quality in the future?

To identify future impacts on biomass production and yield quality of important C3 crops, spring wheat was grown in association with 13 weed species in a Mini-FACE (free-air carbon dioxide (CO2) enrichment) system under ambient (375 μl l-1) and elevated (526 μl l-1) CO2 concentrations. Wheat productivity was assessed at maturity and grain yield was subjected to various chemical analyses and baking quality tests.CO2 enrichment acted as carbon ‘fertiliser’ and increased the aboveground biomass production of wheat by 18.8% as there was a trend towards higher stem biomass. Although not statistically significant, wheat grain yield was increased by 13.4% due to a significant establishment of more grains per unit ground area. At the same time, thousand grain weight was non-significantly shifted towards smaller grain size classes, which may result in negative consequences for the crop market value. As a result of the CO2- induced physiological and biochemical modifications, concentration of total grain protein was significantly decreased by 3.5%, reducing the wheat grain quality with potentially far-reaching impacts on the nutritional value and use for processing industry. Although often not significant, the concentrations of amino acids per unit of flour were decreased by 0.2 to 8.3% due to elevated CO2 thereby affecting the composition of proteinogenic amino acids.Furthermore, gluten proteins tended to decline. Within the significant decreased gliadins, α- and ω5-gliadins were significantly reduced under CO2 enrichment; there was also a negative trend for ω1,2- and γ-gliadins. Changes in certain essential minerals were found as well, although not statistically significant. Concentrations of sodium, calcium, phosphorus and sulphur were slightly lowered and those of potassium and magnesium were slightly increased due to CO2 enrichment. The micro-element molybdenum was increased, while concentrations of iron, zinc, copper, manganese and aluminium were decreased. With regard to rheological and baking parameters defining the cereal quality for industrial processing, the resistance of the dough was significantly reduced by about 30%, while the extensibility was non-significantly increased by 17.1% under CO2 enrichment. Moreover, the bread volume was decreased non-significantly by about 9%. Elevated CO2 is obviously affecting grain characteristics important for consumer nutrition and health, industrial processing and marketing. Experimental evidence for these changes is still poor but deserves further attention

Interactions of Generated Weather Raster and Soil Profiles in Simulating Adaptive Crop Management and Consequent Yields for Five Major Crops throughout a Region in Southern Germany

Klimaanpassung und MitigationThe ability of bioeconomic simulation modelling to realistically predict agricultural adaptation is limited by the degree of detail in crucial model components. Model robustness must be tested before localized calibrations can be applied to regions of heterogenous environmental conditions. The agent-based model FARMACTOR was used to simulate the timing of field management actions (planting, harvest etc.) in response to environmental conditions, and consequent yields of winter wheat, barley and rapeseed, spring barley and silage maize as the predominant crops in a distinct region of Germany, by linking weather data and the crop growth simulation model EXPERT-N. The integrated models were calibrated to observed experimental data and official phenological observations and then run from 1990 to 2009, forced with climate data from ERA-interim Reanalyses data which was downscaled with the Weather and Research Forecast (WRF) model to a 12 X 12 km² grid. Variability in regional soils was replicated with 10 different soil profiles mapped at 1/25,000 scale. The nature of the forcing climate data dictates temporal aggregation for analysis, so that validity is examined by comparing mean simulated planting and harvest dates and yields to official records in the area. The mean predicted planting dates are very close to observations over the period, within a few days of observations, but show less variance. Harvest dates are accurately predicted as well, within one to two weeks, and the variances are closer to observations. Predicted winter wheat yields are well simulated in comparison to observed data, but maize yields are underestimated, while winter and spring barley and winter rapeseed yields are greater than observed district ("Landkreis") yields. The degree of variance in simulated yields is acceptable in wheat, winter barley and maize, but excessive in spring barley and winter rapeseed. Cross-sectional examination of yields shows that the different soil profiles are responsible for more yield variance than simulated weather cells in all crops. While the coupled models appear accurate in predicting crop management dates and physiological development, the inaccuracy in yields in all crops except winter wheat calls into question the reliability of the integrated models when applied, as is, outside of calibration conditions. That soil parameterization is responsible for more variance than generated weather is helpful in seeking to improve performance and encouraging in terms of the method of weather generation. Reliable extension of the coupled models to include all soils in an area together with artificial spatial climatic variability may require regionalized calibration to increase crop model stability

Evaluating multi-year, multi-site data on the energy balance closure of eddy-covariance flux measurements at cropland sites in southwestern Germany

The energy balance of eddy-covariance (EC) measurements is typically not closed, resulting in one of the main challenges in evaluating and interpreting EC flux data. Energy balance closure (EBC) is crucial for validating and improving regional and global climate models. To investigate the nature of the gap in EBC for agroecosystems, we analyzed EC measurements from two climatically contrasting regions (Kraichgau – KR – and Swabian Jura – SJ) in southwestern Germany. Data were taken at six fully equipped EC sites from 2010 to 2017. The gap in EBC was quantified by ordinary linear regression, relating the energy balance ratio (EBR), calculated as the quotient of turbulent fluxes and available energy, to the residual energy term. In order to examine potential reasons for differences in EBC, we compared the EBC under varying environmental conditions and investigated a wide range of possible controls. Overall, the variation in EBC was found to be higher during winter than summer. Moreover, we determined that the site had a statistically significant effect on EBC but no significant effect on either crop or region (KR vs SJ). The time-variable footprints of all EC stations were estimated based on data measured in 2015, complimented by micro-topographic analyses along the prevailing wind direction. The smallest mean annual energy balance gap was 17&thinsp;% in KR and 13&thinsp;% in SJ. Highest EBRs were mostly found for winds from the prevailing wind direction. The spread of EBRs distinctly narrowed under unstable atmospheric conditions, strong buoyancy, and high friction velocities. Smaller footprint areas led to better EBC due to increasing homogeneity. Flow distortions caused by the back head of the anemometer negatively affected EBC during corresponding wind conditions.</p

Simulating regional climate-adaptive field cropping with fuzzy logic management rules and genetic advance.

Agriculture is a largely technical endeavour involving complicated managerial decision-making that affects crop performance. Farm-level modelling integrates crop models with agent behaviour to account for farmer decision-making and complete the representation of agricultural systems. To replicate an important part of agriculture in Central Europe a crop model was calibrated for a unique region&#39;s predominant crops: winter wheat, winter and spring barley, silage maize and winter rapeseed. Their cultivation was then simulated over multiple decades at daily resolution to test validity and stability, while adding the dimension of agent behaviour in relation to environmental and economic conditions. After validation against regional statistics, simulated future weather scenarios were used to forecast crop management and performance under anticipated global change. Farm management and crop genetics were treated as adaptive variables in the milieu of shifting climatic conditions to allow projections of agriculture in the study region into the coming decades

On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modelling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure methods uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (<i>H</i>) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in southwest Germany in 2011, and the performance of the Jarvis and Ball–Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m⁻² (21% of net radiation). Our study shows that it is crucial to account for the uncertainty in EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model–data comparisons

Response of spring crops and associated aphids to elevated atmospheric CO2 concentrations

Having evolved a parasitic relation to their host plants, aphids may serve as indicators of plant responses to environmental changes. The present rise in atmospheric CO2 concentrations is expected to alter plant leaf chemistry and may thus alter host plant – aphid relations. We involved a climate chamber system and used bird cherry-oat aphid (Rhopalosiphum padi L.) and green peach aphid (Myzus persicae S.) and their respective host plants, spring wheat (Triticum aestivum L. cv. “Triso”) and oilseed rape (Brassica napus cv. “Campino”), to elucidate the effects of atmospheric CO2 enrichment on such bitrophic systems. Spring wheat grown at elevated CO2 (600 ppm) generally had greater above ground biomass than plants grown at ambient CO2 (400 ppm). Bird cherry-oat aphid infestation resulted in reduced spring wheat above ground biomass compared to the non-infested control. Relative crop growth rate (RGR) was increased by elevated CO2. In our study, the relative developmental stage (rDS) and intrinsic rate of increase (rm) of the aphids was only slightly and non-signifi cantly increased under elevated atmospheric CO2 conditions. The response of aphid weight and RGR to elevated CO2 differed, increasing by 24% and 18.2% for bird cherry-oat aphid and decreasing by 12% and 12.5% for green peach aphid, respectively. Aphids reared on spring wheat at elevated CO2 had a shorter lifespan, whereas the opposite effect was found for aphids reared on oilseed rape. The average number of nymphs of the two pest species showed both an increase under elevated CO2. No consistent picture emerges from these findings, and further investigation on host – aphid relations under changing atmospheric conditions such as CO2 enrichment appear necessary

Simulation-based projections of crop management and gross margin variance in contrasting regions of Southwest Germany.

Crop simulation is a modern tool used to mimic ordinary and extraordinary agriculture systems. Under the premise of continuing foreseeable climatic shift we combine adaptive field-level management decisions with their effects on crop performance. Price projections are used to examine yield and price effects on gross margins of the predominant crops in two specific regions of Southwest Germany into the coming decades. After calibration and validation to historic records, simulated future weather is used to explore how farmer behavior and performance of wheat, barley, rapeseed and maize could develop under anticipated global change. This development is examined based on a comparison of historic and projected gross margin variance. Simulations indicate that when yield levels increase, the relative variability of gross margins may decline in spite of some increasing variability of yields. The coefficient of variance of gross margins decreases even more due to the independence of price and yield fluctuations. This shows how the effects of global change on yields could be offset by economic conditions

Modeling acclimation of leaf photosynthesis to atmospheric <em>CO₂ </em>enrichment.

In this study, we developed and analyzed a new model for the simulation of photosynthetic active nitrogen (N-P) turnover dynamics in crops and assessed its impact on the acclimation of canopy photosynthesis to atmospheric CO2 enrichment. Typical canopy models assume a vertical exponential decline of light interception following the Beer-Lambert law and vertical distributions of leaf N-P contents directly proportional to the light distribution. This assumption is often inconsistent with experimental observations. We therefore modified and extended the photosynthesis model of the GECROS crop model to consider the trade-off that occurs between the use of degraded N-P for plant growth and the synthesis of new N-P. This model extension thus enabled the examination of the CO2-induced down-regulation of photosynthesis hypothesis using a crop model. The simulation results of the original and modified GECROS model were compared and evaluated based upon measurements of field-grown spring wheat. The modified GECROS model better simulated the dynamics of crop growth under varying atmospheric CO2 concentrations. Furthermore, the application of different temperature functions to N-P degradation strongly influenced the simulation results, revealing the necessity for improving the understanding of the temperature dependence of N-P turnover for different crop species and varieties. In conclusion, the redistribution of nitrogen within the plant and its alternative use either for growth or the optimization of the photosynthetic apparatus is an important mechanism for crop growth acclimation to regionally changing climatic conditions and in particular, atmospheric CO2 enrichment