Investigating Forest Photosynthetic Response to Elevated CO2 Using UAV-Based Measurements of Solar Induced Fluorescence

The response of ecosystems to increasing atmospheric CO2 will have significant, but still uncertain, impacts on the global carbon and water cycles. A lot of infounation has been gained from Free Air CO2 Enrichment (FACE) experiments, but the response of mature forest ecosystems remains a significant knowledge gap. One of the challenges in FACE studies is obtaining an integrated measure of canopy photosynthesis at the scale of the treatment ring. A new remote sensing approach for measuring photosynthetic activity is based on Solar Induced Fluorescence (SIF), which is emitted by plants during photosynthesis, and is closely linked to the rates and regulation of photosynthesis. We proposed that UAV-based SIF measurements, that enable the spectrometer field of view to be targeted to the treatment ring, provide a unique opportunity for investigating the dynamics of photosynthetic responses to elevated CO2. We have successfully tested this approach in a new FACE site, located in a mature oak forest in the UK. We flew a series of flights across the experiment arrays, collecting a number of spectra. We combined these with ground-based physiological and optical measurements, and see great promise in the use of UAV-based SIF measurements in FACE and other global change experiments.Peer reviewe

Effects of exogenous glutathione on suspension callus cells of spruce [Picea abies (L.) Karst.]

Callus cells of Picea abies (L.) Karst, were exposed to different concentrations (50, 100, 500, 1000 μM) of reduced glutathione (GSH) for 48 hours. These physiologically relevant concentrations of glutathione caused changes in the investigated tissue depending on the concentration applied. Feeding of glutathione increased the cellular concentrations of thiols, decreased the rate of cell division, induced mitotic abnormalities, generated increased amounts of micronuclei and affected the cell ultrastructure. The glutathione system in the callus culture cells was measured by a quantitative image analysis method, using histochemical staining by monochlorobimane. This measurement showed an increase of thiols at the cellular level after GSH treatment. Whereas no distinct structural modifications were found in cells treated with 50 and 100 μM, the treatment with 500 and 1000 μM GSH had multiple effects on the investigated tissue in comparison to control cells. Damage observed in the electron microscope involved separation of the plasma membrane from the cell wall, swollen plastids and mitochondria, and heavily granulated chromatin in the nuclei. The investigation of the chromosomal aberrations showed an increased amount of chromosomal defects in the GSH treated cells. The chromosomal aberration types observed most frequently were defects in the form of sticky chromosomes and vagrant chromosomes indicating severe damages in the genetic material

Bark and leaf chlorophyll fluorescence are linked to wood structural changes in Eucalyptus saligna

Wood structure and wood anatomy are usually considered to be largely independent of the physiological processes that govern tree growth. This paper reports a statistical relationship between leaf and bark chlorophyll fluorescence and wood density. A relationship between leaf and bark chlorophyll fluorescence and the quantity of wood decay in a tree is also described. There was a statistically significant relationship between the leaf chlorophyll fluorescence parameter Fv/Fm and wood density and the quantity of wood decay in summer, but not in spring or autumn. Leaf chlorophyll fluorescence at 0.05 ms (the O step) could predict the quantity of wood decay in trees in spring. Bark chlorophyll fluorescence could predict wood density in spring using the Fv/Fm parameter, but not in summer or autumn. There was a consistent statistical relationship in spring, summer and autumn between the bark chlorophyll fluorescence parameter Fv/Fm and wood decay. This study indicates a relationship between chlorophyll fluorescence and wood structural changes, particularly with bark chlorenchyma

Effects of elevated CO2 on chloroplast pigments of spruce (Picea abies) and beech (Fagus sylvatica) in model ecosystems as modified by provenance, soil type, and nitrogen supply

Young beech (Fagus sylvatica L.) and spruce (Picea abies [L,] Karst.) trees, each from two different provenances, were grown in competition in model ecosystems in open-top chambers for four years. The treatments consisted of elevated concentrations of CO, (370 μL L-1 versus 590 μL L-1), increased wet deposition of nitrogen (7 versus 70 kg N ha-1 y-1) and two different forest soils (acidic versus calcareous). Chloroplast pigments in dark- and light-adapted leaf material sampled in the last year of the experiment were analysed. Differences in pigment composition between provenances were observed only in beech trees. Soil type significantly affected the pigment composition in both species. Trees grown under calcareous conditions had higher contents of chlorophylls, whereas acidic soil conditions caused significantly enhanced levels of ß-carotene and xanthophylls as well as increased values of the xanthophyll de-epoxidation status. For both tree species light-adapted samples had higher carotenoid concentrations and de-epoxidation state values than dark-adapted foliage, whereas neither C02 nor N-treatment affected these parameters. Elevated CO, application induced decreased concentrations of total chlorophyll contents in both species. Nitrogen deposition had no effects on pigment composition neither for spruce nor for beech trees. Interactions between CO, and nitrogen application were not observed for both tree species

Elevated atmospheric [CO2] can dramatically increase wheat yields in semi-arid environments and buffer against heat waves

Wheat production will be impacted by increasing concentration of atmospheric CO2 [CO2], which is expected to rise from about 400 μmol mol−1 in 2015 to 550 μmol mol−1 by 2050. Changes to plant physiology and crop responses from elevated [CO2] (e[CO2]) are well documented for some environments, but field-level responses in dryland Mediterranean environments with terminal drought and heat waves are scarce. The Australian Grains Free Air CO2 Enrichment facility was established to compare wheat (Triticum aestivum) growth and yield under ambient (~370 μmol−1 in 2007) and e[CO2] (550 μmol−1) in semi-arid environments. Experiments were undertaken at two dryland sites (Horsham and Walpeup) across three years with two cultivars, two sowing times and two irrigation treatments. Mean yield stimulation due to e[CO2] was 24% at Horsham and 53% at Walpeup, with some treatment responses greater than 70%, depending on environment. Under supplemental irrigation, e[CO2] stimulated yields at Horsham by 37% compared to 13% under rainfed conditions, showing that water limited growth and yield response to e[CO2]. Heat wave effects were ameliorated under e[CO2] as shown by reductions of 31% and 54% in screenings and 10% and 12% larger kernels (Horsham and Walpeup). Greatest yield stimulations occurred in the e[CO2] late sowing and heat stressed treatments, when supplied with more water. There were no clear differences in cultivar response due to e[CO2]. Multiple regression showed that yield response to e[CO2] depended on temperatures and water availability before and after anthesis. Thus, timing of temperature and water and the crop's ability to translocate carbohydrates to the grain postanthesis were all important in determining the e[CO2] response. The large responses to e[CO2] under dryland conditions have not been previously reported and underscore the need for field level research to provide mechanistic understanding for adapting crops to a changing climate

Elevated atmospheric [CO₂] can dramatically increase wheat yields in semi-arid environments and buffer against heat waves

Tausz, M ORCiD: 0000-0001-8205-8561Wheat production will be impacted by increasing concentration of atmospheric CO2 [CO2], which is expected to rise from about 400 μmol mol-1 in 2015 to 550 μmol mol-1 by 2050. Changes to plant physiology and crop responses from elevated [CO2] (e[CO2]) are well documented for some environments, but field-level responses in dryland Mediterranean environments with terminal drought and heat waves are scarce. The Australian Grains Free Air CO2 Enrichment facility was established to compare wheat (Triticum aestivum) growth and yield under ambient (~370 μmol-1 in 2007) and e[CO2] (550 μmol-1) in semi-arid environments. Experiments were undertaken at two dryland sites (Horsham and Walpeup) across three years with two cultivars, two sowing times and two irrigation treatments. Mean yield stimulation due to e[CO2] was 24% at Horsham and 53% at Walpeup, with some treatment responses greater than 70%, depending on environment. Under supplemental irrigation, e[CO2] stimulated yields at Horsham by 37% compared to 13% under rainfed conditions, showing that water limited growth and yield response to e[CO2]. Heat wave effects were ameliorated under e[CO2] as shown by reductions of 31% and 54% in screenings and 10% and 12% larger kernels (Horsham and Walpeup). Greatest yield stimulations occurred in the e[CO2] late sowing and heat stressed treatments, when supplied with more water. There were no clear differences in cultivar response due to e[CO2]. Multiple regression showed that yield response to e[CO2] depended on temperatures and water availability before and after anthesis. Thus, timing of temperature and water and the crop's ability to translocate carbohydrates to the grain postanthesis were all important in determining the e[CO2] response. The large responses to e[CO2] under dryland conditions have not been previously reported and underscore the need for field level research to provide mechanistic understanding for adapting crops to a changing climate. © 2016 John Wiley & Sons Ltd

Using an optimality model to understand medium and long-term responses of vegetation water use to elevated atmospheric CO2 concentrations

Vegetation has different adjustable properties for adaptation to its environment. Examples include stomatal conductance at short time scale (minutes), leaf area index and fine root distributions at longer time scales (days-months) and species compositio

Characteristics of free air carbon dioxide enrichment of a northern temperate mature forest

Tausz, M ORCiD: 0000-0001-8205-8561In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large scale infrastructure, in the form of lattice towers, forming 'arrays' which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO2 concentrations (e[CO2 ]) by +150 μmol mol-1 . In practice, acceptable operational enrichment (ambient [CO2 ] + e[CO2 ]) is ± 20% of the set-point 1-minute average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO2 ] (April to November 2017), [CO2 ] measurements in treatment and control arrays show that the target concentration was successfully delivered, i.e.: +147 ± 21 μmol mol-1 (mean ± SD) or 98 ± 14% of set-point enrichment target. e[CO2 ] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO2 supply issues (0.6%), or adverse weather conditions (1.1%). CO2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO2 occurred  80 μmol mol-1 (i.e., > 53% of the treatment increment) into control arrays accounted for < 0.1% of the enrichment period. The median [CO2 ] values in reconstructed 3-dimensional [CO2 ] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next-generation forest FACE facilities built into tall and complex forest stands. This article is protected by copyright. All rights reserved

Elevated [CO2 ] effects on crops: Advances in understanding acclimation, nitrogen dynamics and interactions with drought and other organisms

Tausz, M ORCiD: 0000-0001-8205-8561Future rapid increases in atmospheric CO2 concentration [CO2 ] are expected, with values likely to reach ~550 ppm by mid-century. This implies that every terrestrial plant will be exposed to nearly 40% more of one of the key resources determining plant growth. In this review we highlight selected areas of plant interactions with elevated [CO2 ] (e[CO2 ]), where recently published experiments challenge long-held, simplified views. Focusing on crops, especially in more extreme and variable growing conditions, we highlight uncertainties associated with four specific areas: (1) While it is long known that photosynthesis can acclimate to e[CO2 ], such acclimation is not consistently observed in field experiments. The influence of sink-source relations and nitrogen (N) limitation on acclimation is investigated and current knowledge about whether stomatal function or mesophyll conductance (gm ) acclimate independently is summarised. (2) We show how the response of N uptake to e[CO2 ] is highly variable, even for one cultivar grown within the same field site, and how decreases in N concentrations ([N]) are observed consistently. Potential mechanisms contributing to [N] decreases under e[CO2 ] are discussed and proposed solutions are addressed. (3) Based on recent results from crop field experiments in highly variable, non-irrigated, water-limited environments, we challenge the previous opinion that the relative CO2 effect is greater under drier environmental conditions. (4) Finally, we summarise how changes in growth and nutrient concentrations due to e[CO2 ] will influence relationships between crops and weeds, herbivores and pathogens in agricultural systems. This article is protected by copyright. All rights reserved