Search

Increasing atmospheric CO2 enhances plant biomass production and may thereby change nutrient concentrations in plant tissues. The objective of this study was to identify the effect of elevated atmospheric CO2 concentrations on nutrient concentrations of grassland biomass that have been grown for 16 years (1998–2013). The grassland biomass grown at the extensively managed Giessen FACE experiment, fumigated with ambient and elevated CO2 (aCO2; eCO2; +20%) was harvested twice annually. Concentrations of C, N, P, K, Ca, Mg, Mn, Fe, Cu and Zn were determined separately for grasses, forbs and legumes. Under eCO2, the concentration of N was reduced in grasses, Ca was reduced in grasses and forbs, P was reduced in grasses but increased in legumes, Mg concentration was reduced in grasses, forbs and legumes and K was reduced in grasses but increased in forbs. The nutrient yield (in g nutrient yield of an element per m−2) of most elements indicated negative yield responses at a zero biomass response to eCO2 for grasses. K and Zn nutrient yields responded positively to eCO2 in forbs and Mn and Fe responded positively in forbs and legumes. The results suggest that under eCO2 the nutrient concentrations were not diluted by the CO2 fertilization effect. Rather, altered plant nutrient acquisitions via changed physiological mechanisms prevail for increased C assimilation under eCO2. Furthermore, other factors such as water or nutrient availability affected plant nutrient concentrations under eCO2. [ABSTRACT FROM AUTHOR]

Increasing CO2 concentration ([CO2]) is thought to induce climate change and thereby increase air temperatures and the risk of drought stress, the latter impairing crop growth. The objective of this study was to investigate the effects of elevated [CO2] and drought stress on root growth of one maize genotype (Zea mays cv. Simao) and two sorghum genotypes (Sorghum bicolor cv. Bulldozer and Sorghum bicolor × Sorghum sudanense cv. Inka) under the cool moderate climate of Central Europe. It was hypothesized that root growth stimulation due to elevated [CO2] compensates for a reduced root growth under drought stress. Therefore, we established an experiment within a free‐air carbon dioxide enrichment system (FACE) in 2010 and 2011. Sorghum and maize genotypes were grown under ambient [CO2] (385 ppm CO2) and elevated [CO2] (600 ppm CO2) and in combination with restricted and sufficient water supply. Elevated [CO2] decreased root length density (RLD) in the upper soil layers for all genotypes, but increased it in deeper layers. Higher [CO2] enhanced specific root length (SRL) of "Simao" and "Bulldozer," however, did not affect that of "Inka." "Simao" achieved a higher SRL than the sorghum genotypes, indicating an efficient investment in root dry matter. Although elevated [CO2] affected the root growth, no interaction with the water treatment and, consequently, no compensatory effect of elevated [CO2] could be identified. [ABSTRACT FROM AUTHOR]

Abstract: Future increase in atmospheric CO2 concentrations will potentially enhance grassland biomass production and shift the functional group composition with consequences for ecosystem functioning. In the “GiFACE” experiment (Giessen Free Air Carbon dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO2 (eCO2) year‐round during daylight hours since 1998, at a level of +20% relative to ambient concentrations (in 1998, aCO2 was 364 ppm and eCO2 399 ppm; in 2014, aCO2 was 397 ppm and eCO2 518 ppm). Harvests were conducted twice annually through 23 years including 17 years with eCO2 (1998 to 2014). Biomass consisted of C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass (TAB) was significantly increased under eCO2 (p = .045 and .025, at first and second harvest). The dominant plant functional group grasses responded positively at the start, but for forbs, the effect of eCO2 started out as a negative response. The increase in TAB in response to eCO2 was approximately 15% during the period from 2006 to 2014, suggesting that there was no attenuation of eCO2 effects over time, tentatively a consequence of the fertilization management. Biomass and soil moisture responses were closely linked. The soil moisture surplus (c. 3%) in eCO2 manifested in the latter years was associated with a positive biomass response of both functional groups. The direction of the biomass response of the functional group forbs changed over the experimental duration, intensified by extreme weather conditions, pointing to the need of long‐term field studies for obtaining reliable responses of perennial ecosystems to eCO2 and as a basis for model development. [ABSTRACT FROM AUTHOR]

A 2-year Free Air CO2 Enrichment ( FACE) experiment was conducted with winter wheat. It was investigated whether elevated atmospheric CO2 concentration (e[ CO2]) inhibit nitrate assimilation and whether better growth and nitrogen acquisition under e[ CO2] can be achieved with an ammonium-based fertilization as it was observed in hydroponic culture with wheat. Under e[ CO2] a decrease in nitrate assimilation has been discussed as the cause for observed declines in protein concentration in C3 cereals. Wheat was grown under ambient [ CO2] and e[ CO2] (600 ppm) with three levels (deficiency, optimal, and excessive) of nitrate-based fertilization (calcium ammonium nitrate; CAN) or with optimal ammonium-based fertilization. Ammonium fertilization was applied via injection of an ammonium solution into the soil in the 1st year and by surface application of urea combined with nitrification inhibitors ( UNI) in the 2nd year. Results showed that ammonium-based fertilization was successfully achieved in the 2nd year with respect to nitrification control, as soil ammonium concentration was considerably higher over the growing season for UNI fertilized plots compared to optimal CAN plots. Also, stem nitrate concentration, flag leaf nitrate reductase activity, and transcript levels were lower in UNI fertilized plants compared to optimal CAN. Regarding the e[ CO2] effect on nitrate reductase activity and transcript levels, no alteration could be observed for any nitrogen fertilizer treatment. Flag leaf growth was stimulated under e[ CO2] leading to an enhanced nitrate reductase activity referred to m2 ground area at late flowering being in line with a higher nitrogen acquisition under e[ CO2]. Moreover, nitrogen acquisition was considerably higher in nitrate fertilized plants compared to ammonium fertilized plants under e[ CO2]. Our results obtained under field conditions show that a change from nitrate- to ammonium-based fertilization will not lead to a better growth and nitrogen acquisition of winter wheat under future e[ CO2]. [ABSTRACT FROM AUTHOR]

Elevated CO2 ( eCO2) concentrations can stimulate crop growth, but little is known about intraspecific variability in the response to eCO2 and the underlying genetics in cereals. Field experiments over two years with 98 barley genotypes were conducted in open-top chambers ( OTCs) under ambient CO2 (400 ppm) and eCO2 (700 ppm) concentrations. At crop maturity, different fractions of aboveground biomass ( AGB) were measured, and genome-wide association studies ( GWASs) were conducted to identify quantitative trait loci ( QTL). Averaged across all genotypes, eCO2 significantly enhanced AGB by 15%, while the increase in culm and ear biomass alone was not significant. The AGB response to eCO2 of the individual genotypes ranged from c. −36% to +95% compared with ambient CO2 ( aCO2), showing a large variability of growth responses. In GWAS, 51 associations between SNP markers and the relative changes ( eCO2/ aCO2) in biomass were detected on different chromosomes. Loci potentially involved in biomass alterations under eCO2 were identified. The wide range of variability in responses might be exploited by marker-based breeding for climate-resilient barley. [ABSTRACT FROM AUTHOR]

Abstract: Predicting future maize yields requires quantifying anticipated climate change impacts on maize growth and yield. In the present study, maize was grown over 2 years (2007 and 2008) under sufficient (WET) and reduced water supply (DRY) and under ambient (378μll−1, AMB) and elevated (550μll−1, FACE) atmospheric CO2 concentration ([CO2]) using free air CO2 enrichment (FACE). The objective of the present study was to test the hypothesis that maize growth does not respond to elevated [CO2] under WET but under DRY conditions due to an increase of water use efficiency (WUE) of biomass production realized through reduced transpiration. Moreover, in 2008 soil cover was varied to test whether mitigation of evaporation by straw mulch increases the CO2 effect on WUE. The DRY treatment received 12% and 48% less water than the WET treatment in 2007 and 2008, respectively, which was achieved with the aid of rainout shelters. In the first year, drought stress was insignificant and crop growth was similar among the two watering regimes. CO2 enrichment did not affect crop growth in 2007 and also in the WET treatment of 2008. In the second year, a pronounced drought stress decreased green leaf index, accumulated seasonal radiation absorption and radiation use efficiency (RUE) significantly. However, these effects were mitigated by CO2 enrichment and the decrease of RUE was higher under AMB (−18%) than under FACE (−2%) conditions. In the DRY treatment in 2008, CO2 enrichment significantly increased final biomass (+24%) and grain yield (+41%) as compared to the DRY AMB treatment. CO2 enrichment significantly increased soil water content under WET and DRY conditions but did not affect the soil water exploitation. There was a significant interaction of [CO2] and water supply on WUE with no (2007) or a small CO2-response (+10% in 2008) under WET and a strong effect under DRY conditions in 2008 (+25%). Soil cover did not intensify the CO2 effect on WUE. It is concluded that maize will benefit from the increase in [CO2] only under drought but not under sufficient water supply. [Copyright &y& Elsevier]

The influence of elevated atmospheric CO2 concentrations ([CO2]) on the decomposition of spring wheat (Triticum aestivum L. cv. Triso) residues remaining in the soil after harvest was simulated in a microcosm incubation experiment in the lab. Undisturbed soil cores with and without visible wheat residues were taken in the third year after establishment from a Mini-free-air carbon dioxide enrichment (FACE) system, in which we used 13C-depleted CO2 to determine the contribution of plant-derived carbon to overall carbon mineralization. The Mini-FACE system is located on a Gleyic Cambisol near Hohenheim (Baden-Württemberg, Germany). Carbon dioxide production and leaching of nitrogen and inorganic and organic carbon were measured during 191 days of incubation. Rates of CO2 production were generally highest in all treatments during the first two weeks of the incubation and this was followed by a steady decrease until day 58. After this day mineralization rates declined only weakly until the end of the incubation. Cumulative carbon mineralization was similar in the two treatments without visible wheat residues, but significantly lower in the elevated (−19.0%) versus ambient [CO2] treatment with visible plant residues (significant [CO2]×residue interaction; F 1,13 =7.17; P =0.019). This result demonstrated reduced decomposition of wheat residues grown under elevated [CO2]. The contribution of plant-derived carbon to soil respiration was highest in the beginning, followed by a steady decrease until the end of the incubation. Irrespective of incubation time, the amount of mineralized, plant-derived carbon was higher in the treatment with visible wheat residues. Leaching of inorganic carbon (DIC) tended to be affected by [CO2] (F 6,8 =4.50; P =0.057), with more DIC leached in the elevated [CO2] treatment without (+47.2%) and with visible plant residues (+29.5%) than in the respective ambient CO2 treatments. The amount of carbon potentially sequestered as DIC in the wheat cropping system was small compared to the effects of elevated [CO2] on the amounts and decomposition of plant residues. Increased input of plant residues and reduced decomposition of plant-derived carbon are discussed as possible mechanisms for enhanced carbon sequestration under elevated atmospheric CO2 concentration. [Copyright &y& Elsevier]

Abstract: Future increase in atmospheric CO2 concentrations will potentially enhance grassland biomass production and shift the functional group composition with consequences for ecosystem functioning. In the “GiFACE” experiment (Giessen Free Air Carbon dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO2 (eCO2) year‐round during daylight hours since 1998, at a level of +20% relative to ambient concentrations (in 1998, aCO2 was 364 ppm and eCO2 399 ppm; in 2014, aCO2 was 397 ppm and eCO2 518 ppm). Harvests were conducted twice annually through 23 years including 17 years with eCO2 (1998 to 2014). Biomass consisted of C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass (TAB) was significantly increased under eCO2 (p = .045 and .025, at first and second harvest). The dominant plant functional group grasses responded positively at the start, but for forbs, the effect of eCO2 started out as a negative response. The increase in TAB in response to eCO2 was approximately 15% during the period from 2006 to 2014, suggesting that there was no attenuation of eCO2 effects over time, tentatively a consequence of the fertilization management. Biomass and soil moisture responses were closely linked. The soil moisture surplus (c. 3%) in eCO2 manifested in the latter years was associated with a positive biomass response of both functional groups. The direction of the biomass response of the functional group forbs changed over the experimental duration, intensified by extreme weather conditions, pointing to the need of long‐term field studies for obtaining reliable responses of perennial ecosystems to eCO2 and as a basis for model development. [ABSTRACT FROM AUTHOR]

Elevated atmospheric CO 2 concentrations (e[CO 2 ]) can decrease the grain quality of wheat. However, little information exists concerning interactions between e[CO 2 ] and nitrogen fertilization on important grain quality traits. To investigate this, a 2-year free air CO 2 enrichment (FACE) experiment was conducted with two CO 2 (393 and 600 ppm) and three (deficiency, adequate, and excess) nitrogen levels. Concentrations of flour proteins (albumins/globulins, gliadins, and glutenins) and key minerals (iron, zinc, and sulfur) and baking quality (loaf volume) were markedly increased by increasing nitrogen levels and varied between years. e[CO 2 ] resulted in slightly decreased albumin/globulin and total gluten concentration under all nitrogen conditions, whereas loaf volume and mineral concentrations remained unaffected. Two-dimensional gel electrophoresis revealed strong effects of nitrogen supply and year on the grain proteome. Under adequate nitrogen, the grain proteome was affected by e[CO 2 ] with 19 downregulated and 17 upregulated protein spots. The downregulated proteins comprised globulins but no gluten proteins. e[CO 2 ] resulted in decreased crude protein concentration at maximum loaf volume. The present study contrasts with other FACE studies showing markedly stronger negative impacts of e[CO 2 ] on chemical grain quality, and the reasons for that might be differences between genotypes, soil conditions, or the extent of growth stimulation by e[CO 2 ].

Future increase in atmospheric CO 2 concentrations will potentially enhance grassland biomass production and shift the functional group composition with consequences for ecosystem functioning. In the "GiFACE" experiment (Giessen Free Air Carbon dioxide Enrichment), fertilized grassland plots were fumigated with elevated CO 2 (eCO 2 ) year-round during daylight hours since 1998, at a level of +20% relative to ambient concentrations (in 1998, aCO 2 was 364 ppm and eCO 2 399 ppm; in 2014, aCO 2 was 397 ppm and eCO 2 518 ppm). Harvests were conducted twice annually through 23 years including 17 years with eCO 2 (1998 to 2014). Biomass consisted of C3 grasses and forbs, with a small proportion of legumes. The total aboveground biomass (TAB) was significantly increased under eCO 2 (p = .045 and .025, at first and second harvest). The dominant plant functional group grasses responded positively at the start, but for forbs, the effect of eCO 2 started out as a negative response. The increase in TAB in response to eCO 2 was approximately 15% during the period from 2006 to 2014, suggesting that there was no attenuation of eCO 2 effects over time, tentatively a consequence of the fertilization management. Biomass and soil moisture responses were closely linked. The soil moisture surplus (c. 3%) in eCO 2 manifested in the latter years was associated with a positive biomass response of both functional groups. The direction of the biomass response of the functional group forbs changed over the experimental duration, intensified by extreme weather conditions, pointing to the need of long-term field studies for obtaining reliable responses of perennial ecosystems to eCO 2 and as a basis for model development., (© 2017 John Wiley & Sons Ltd.)