Future Elevated CO2 Concentrations Research Articles

Mating still disrupted: Future elevated CO<sub>2</sub> concentrations are likely to not interfere with <i>Lobesia botrana</i> and <i>Eupoecilia ambiguella</i> mating disruption in vineyards in the near future

The successful, area-wide application of the mating disruption (MD) technique, an insect sex pheromone-based biotechnological pest control method, against the European grapevine moth Lobesia botrana and the European grape berry moth Eupoecilia ambiguella, has led to drastic reductions in insecticide application in vineyards. However, since insect pheromone perception and emission can be affected by abiotic conditions, the future success of MD may be affected by climate change. At the same time, politics and society are calling for drastic and sustainable reductions in pesticide application, making highly specific, efficient, and environmentally friendly pest control techniques like MD more important than ever. To anticipate whether climate change factors will interfere with the MD of L. botrana and E. ambiguella in vineyards, we conducted field experiments in the Geisenheim VineyardFACE (Free-Air Carbon dioxide Enrichment) facility. The insects were raised at ambient or elevated temperatures in the lab and male moths were released in cages installed in the VineyardFACE facility. Trap recapture rates obtained by pheromone lures or female moths under elevated or ambient CO2 in areas with and without MD were evaluated. Our results did not indicate a reduced efficacy ofL. botrana or E. ambiguella MD at elevated CO2 concentrations, irrespective of the temperature the moths were raised under. From a practical point of view—and especially from an ecological one—our results are good news. They indicate that MD will not be negatively affected by future elevated CO2 concentrations.

Evapotranspiration of Irrigated Crops under Warming and Elevated Atmospheric CO2: What Is the Direction of Change?

Future changes in crop evapotranspiration (ETc) are of interest to water management stakeholders. However, long-term projections are complex and merit further investigation due to uncertainties in climate data, differential responses of crops to climate and elevated atmospheric CO2, and adaptive agricultural management. We conducted factor-control simulation experiments using the process-based CropSyst model and investigated the contribution of each of these factors. Five major irrigated crops in the Columbia Basin Project area of the USA Pacific Northwest were selected as a case study and fifteen general circulation models (GCM) under two representative concentration pathways (RCP) were used as the climate forcing. Results indicated a wide range in ETc change, depending on the time frame, crop type, planting dates, and CO2 assumptions. Under the 2090s RCP8.5 scenario, ETc changes were crop-specific: +14.3% (alfalfa), +8.1% (potato), −5.1% (dry bean), −8.1% (corn), and −12.5% (spring wheat). Future elevated CO2 concentrations decreased ETc for all crops while earlier planting increased ETc for all crops except spring wheat. Changes in reference ET (ETo) only partially explains changes in ETc because crop responses are an important modulating factor; therefore, caution must be exercised in interpreting ETo changes as a proxy for ETc changes.

Elevated atmospheric CO2 concentrations alter grapevine (Vitis vinifera) systemic transcriptional response to European grapevine moth (Lobesia botrana) herbivory

Atmospheric carbon dioxide (CO2) concentrations are among the chief factors shaping the mode and magnitude of interactions between plants and herbivorous insects. Here, we describe the first global analysis of systemic transcriptomic responses of grapevine Vitis vinifera plants to feeding of European grapevine moth Lobesia botrana larvae at future elevated CO2 concentrations. The study was conducted on mature, fruit-bearing grapevine plants under ambient and elevated CO2 concentrations in a grapevine free-air carbon dioxide enrichment (FACE) facility. Grapevine transcriptional response to herbivory was clearly dependent on phenological stage, with a higher number of differentially expressed genes identified at fruit development compared to berry ripening. At fruit development, more transcripts were differentially expressed as a response to herbivory under elevated compared to ambient CO2 concentrations. Classification of the respective transcripts revealed that in particular genes involved in metabolic pathways, biosynthesis of secondary metabolites and plant-pathogen interactions were significantly enriched. Most of these genes had similar expression patterns under both CO2 concentrations, with a higher fold-change under elevated CO2 concentrations. Differences in expression levels of a subset of herbivory responsive genes were further validated by RT-qPCR. Our study indicates that future elevated CO2 concentrations will affect interactions between grapevine plants and one of its key insect pests, with consequences for future relevance of L. botrana in worldwide viticulture.

The optimal CO2 concentrations for the growth of three perennial grass species

BackgroundGrasslands are one of the most representative vegetation types accounting for about 20% of the global land area and thus the response of grasslands to climate change plays a pivotal role in terrestrial carbon balance. However, many current climate change models, based on earlier results of the doubling-CO2 experiments, may overestimate the CO2 fertilization effect, and as a result underestimate the potentially effects of future climate change on global grasslands when the atmospheric CO2 concentration goes beyond the optimal level. Here, we examined the optimal atmospheric CO2 concentration effect on CO2 fertilization and further on the growth of three perennial grasses in growth chambers with the CO2 concentration at 400, 600, 800, 1000, and 1200 ppm, respectively.ResultsAll three perennial grasses featured an apparent optimal CO2 concentration for growth. Initial increases in atmospheric CO2 concentration substantially enhanced the plant biomass of the three perennial grasses through the CO2 fertilization effect, but this CO2 fertilization effect was dramatically compromised with further rising atmospheric CO2 concentration beyond the optimum. The optimal CO2 concentration for the growth of tall fescue was lower than those of perennial ryegrass and Kentucky bluegrass, and thus the CO2 fertilization effect on tall fescue disappeared earlier than the other two species. By contrast, the weaker CO2 fertilization effect on the growth of perennial ryegrass and Kentucky bluegrass was sustained for a longer period due to their higher optimal CO2 concentrations than tall fescue. The limiting effects of excessively high CO2 concentrations may not only associate with changes in the biochemical and photochemical processes of photosynthesis, but also attribute to the declines in stomatal conductance and nitrogen availability.ConclusionsIn this study, we found apparent differences in the optimal CO2 concentrations for the growth of three grasses. These results suggest that the growth of different types of grasses may respond differently to future elevated CO2 concentrations through the CO2 fertilization effect, and thus potentially alter the community composition and structure of grasslands. Meanwhile, our results may also be helpful for improving current process-based ecological models to more accurately predict the structure and function of grassland ecosystems under future rising atmospheric CO2 concentration and climate change scenarios.

Effects of elevated CO<sub>2</sub> and N fertilization on plant and soil carbon pools of managed grasslands: a meta-analysis

Abstract. Elevated atmospheric CO2 levels and increasing nitrogen deposition both stimulate plant production in terrestrial ecosystems. Moreover, nitrogen deposition could alleviate an increasing nitrogen limitation experienced by plants exposed to elevated CO2 concentrations. However, an increased rate of C flux through the soil compartment as a consequence of elevated CO2 concentrations has been suggested to limit C sequestration in terrestrial ecosystems, questioning the potential for terrestrial C uptake to mitigate increasing atmospheric CO2 concentrations. Our study used data from 77 published studies applying elevated CO2 and/or N fertilization treatment to monitor carbon storage potential in grasslands, and considered the influence of management practices involving biomass removal or irrigation on the elevated CO2 effects. Our results confirmed a positive effect of elevated CO2 levels and nitrogen fertilization on plant growth, but revealed that N availability is essential for the increased C influx under elevated CO2 to propagate into belowground C pools. However, moderate nutrient additions also promoted decomposition processes in elevated CO2, reducing the potential for increased soil C storage. An important role was attributed to the CO2 response of root biomass in soil carbon responses to elevated CO2, since there was a lower potential for increases in soil C content when root biomass increased. Future elevated CO2 concentrations and increasing N deposition might thus increase C storage in plant biomass, but the potential for increased soil C storage is limited.

The performance of Brevicoryne brassicae on ornamental cabbages grown in CO2-enriched atmospheres

The effect of different atmospheric CO2 concentrations on life table parameters and the biology of the cabbage aphid, Brevicoryne brassicae, when fed on two cultivars of ornamental cabbage, was studied in a greenhouse designed for CO2 studies. Aphid performance was influenced by increasing atmospheric CO2 levels, significantly affecting the intrinsic rate of increase (rm), finite rate of increase (λ), mean generation time (T), doubling time (DT), and pre-reproductive period. The longest pre-reproductive period was observed for aphids grown at 380ppm CO2. The intrinsic rate of natural increase was highest for aphids at 1050ppm CO2, because of their faster development, high daily rate of progeny production, and higher survivorship. Future elevated CO2 concentrations will enhance aphid population outbreaks and consequently increase the damage caused.

Crown architecture of Populus spp. is differentially modified by free‐air CO2 enrichment (POPFACE)

Summary Although canopy architecture is a prime determinant of forest functioning and productivity, it has received little attention when examining forest responses to rising atmospheric CO2 concentrations. In this study different characteristics of crown architecture of two Populus species and one hybrid were investigated within a high‐density poplar plantation. A free‐air CO2 enrichment (FACE) facility was used to mimic future elevated CO2 concentrations. Canopy depth and branching patterns were studied, and detailed branch characteristics such as branch dimension, inclination, and internodal length were assessed for the three poplar species in the FACE and control treatments. Effects of elevated CO2 were restricted to a significantly increased canopy depth and longer internodal lengths after two years of CO2 enrichment. Additionally, branch dimensions and sylleptic branch numbers were increased by FACE, but responses were variable among growing seasons and species. However, FACE did not affect branch angles of origin and termination. Crown architecture was modified mainly through a growth stimulation in response to FACE. Nevertheless, important differences among species were observed which may influence future CO2 responses when competition will become more important.

Elevated CO2, drought and soil nitrogen effects on wheat grain quality

Summary The likely consequences of future high levels of atmospheric CO2 concentration on wheat (Triticum aestivum L.) grain nutritional and baking quality were determined. Two free‐air CO2 enrichment (FACE; 550 mmol mol−1) experiments were conducted at ample (Wet) and limiting (Dry) levels of irrigation, and a further two experiments at ample (High‐N) and limiting (Low‐N) nitrogen concentrations. Harvested grain samples were subjected to a battery of nutritional and bread‐making quality tests. The Dry treatment improved grain quality slightly (protein +2%; bread loaf volume +3%). By contrast, Low‐N decreased quality drastically (protein −36%; loaf volume −26%). At ample water and N, FACE decreased quality slightly (protein −5%; loaf volume −2%) in the irrigation experiments and there was no change in the nitrogen experiments. At Low‐N, FACE tended to make the deleterious effects of Low‐N worse (protein −33% and −39%, at ambient CO2 and FACE, respectively; loaf volume −22% and −29% at ambient CO2 and FACE, respectively). The data suggest that future elevated CO2 concentrations will exacerbate the deleterious effects of low soil nitrogen on grain quality, but with ample nitrogen fertilizer, the effects will be minor.