On the variation of regional CO2 exchange over temperate and boreal North America
Zhang, X. ; Gurney, K.R. ; Peylin, P. ; Chevallier, F. ; Law, R.M. ; Patra, P.K. ; Rayner, P.J. ; Roedenbeck, C. ; Krol, M.C. - \ 2013
Global Biogeochemical Cycles 27 (2013)4. - ISSN 0886-6236 - p. 991 - 1000.
atmospheric carbon-dioxide - terrestrial ecosystems - united-states - interannual variability - climate - forest - trends - drought - fluxes - land
Inverse-estimated net carbon exchange time series spanning two decades for six North American regions are analyzed to examine long-term trends and relationships to temperature and precipitation variations. Results reveal intensification of carbon uptake in eastern boreal North America (0.1 PgC/decade) and the Midwest United States (0.08 PgC/decade). Seasonal cross-correlation analysis shows a significant relationship between net carbon exchange and temperature/precipitation anomalies during the western United States growing season with warmer, dryer conditions leading reduced carbon uptake. This relationship is consistent with global change-type drought dynamics which drive increased vegetation mortality, increases in dry woody material, and increased wildfire occurrence. This finding supports the contention that future climate change may increase carbon loss in this region. Similarly, higher temperatures and reduced precipitation are accompanied by decreased net carbon uptake in the Midwestern United States toward the end of the growing season. Additionally, intensified net carbon uptake during the eastern boreal North America growing season is led by increased precipitation anomalies in the previous year, suggesting the influence of climate memory carried by regional snowmelt water. The two regions of boreal North America exhibit opposing seasonal carbon-temperature relationships with the eastern half experiencing a net carbon loss with near coincident increases in temperature and the western half showing increased net carbon uptake. The carbon response in the boreal west region lags the temperature anomalies by roughly 6months. This opposing carbon-temperature relationship in boreal North America may be a combination of different dominant vegetation types, the amount and timing of snowfall, and temperature anomaly differences across boreal North America.
The importance of crop growth modeling to interpret the ¿14CO2 signature of annual plants
Bozhinova, D.N. ; Combe, M. ; Palstra, S.W.L. ; Meijer, H.A.J. ; Krol, M.C. ; Peters, W. - \ 2013
Global Biogeochemical Cycles 27 (2013)3. - ISSN 0886-6236 - p. 792 - 803.
fossil-fuel co2 - atmospheric carbon-dioxide - c-14 - (co2)-c-14 - radiocarbon - netherlands - exchange - records - yield
 The 14C/C abundance in CO2(¿14CO2) promises to provide useful constraints on regional fossil fuel emissions and atmospheric transport through the large gradients introduced by anthropogenic activity. The currently sparse atmospheric ¿14CO2 monitoring network can potentially be augmented by using plant biomass as an integrated sample of the atmospheric ¿14CO2. But the interpretation of such an integrated sample requires knowledge about the day¿to¿day CO2 uptake of the sampled plants. We investigate here the required detail in daily plant growth variations needed to accurately interpret regional fossil fuel emissions from annual plant samples. We use a crop growth model driven by daily meteorology to reproduce daily fixation of ¿14CO2 in maize and wheat plants in the Netherlands in 2008. When comparing the integrated ¿14CO2 simulated with this detailed model to the values obtained when using simpler proxies for daily plant growth (such as radiation and temperature), we find differences that can exceed the reported measurement precision of ¿14CO2(~2‰). Furthermore, we show that even in the absence of any spatial differences in fossil fuel emissions, differences in regional weather can induce plant growth variations that result in spatial gradients of up to 3.5‰ in plant samples. These gradients are even larger when interpreting separate plant organs (leaves, stems, roots, or fruits), as they each develop during different time periods. Not accounting for these growth¿induced differences in ¿14CO2 in plant samples would introduce a substantial bias (1.5–2¿ppm) when estimating the fraction of atmospheric CO2 variations resulting from nearby fossil fuel emissions
Photosynthetic control of electron transport and the regulation of gene expression
Foyer, C.H. ; Neukermans, J. ; Queval, G. ; Noctor, G. ; Harbinson, J. - \ 2012
Journal of Experimental Botany 63 (2012)4. - ISSN 0022-0957 - p. 1637 - 1661.
atmospheric carbon-dioxide - long-term exposure - water-water cycle - ribulose-1,5-bisphosphate carboxylase-oxygenase - excess excitation-energy - ultraviolet-b radiation - nitrogen-use efficiency - mg-protoporphyrin ix - co2 enrichment face - photosystem-i
The term ‘photosynthetic control’ describes the short- and long-term mechanisms that regulate reactions in the photosynthetic electron transport (PET) chain so that the rate of production of ATP and NADPH is coordinated with the rate of their utilization in metabolism. At low irradiances these mechanisms serve to optimize light use efficiency, while at high irradiances they operate to dissipate excess excitation energy as heat. Similarly, the production of ATP and NADPH in ratios tailored to meet demand is finely tuned by a sophisticated series of controls that prevents the accumulation of high NAD(P)H/NAD(P) ratios and ATP/ADP ratios that would lead to potentially harmful over-reduction and inactivation of PET chain components. In recent years, photosynthetic control has also been extrapolated to the regulation of gene expression because mechanisms that are identical or similar to those that serve to regulate electron flow through the PET chain also coordinate the regulated expression of genes encoding photosynthetic proteins. This requires coordinated gene expression in the chloroplasts, mitochondria, and nuclei, involving complex networks of forward and retrograde signalling pathways. Photosynthetic control operates to control photosynthetic gene expression in response to environmental and metabolic changes. Mining literature data on transcriptome profiles of C3 and C4 leaves from plants grown under high atmospheric carbon dioxide (CO2) levels compared with those grown with ambient CO2 reveals that the transition to higher photorespiratory conditions in C3 plants enhances the expression of genes associated with cyclic electron flow pathways in Arabidopsis thaliana, consistent with the higher ATP requirement (relative to NADPH) of photorespiration.
Challenges for weed management in African rice systems in a changing climate
Rodenburg, J. ; Meinke, H.B. ; Johnson, D.E. - \ 2011
The Journal of Agricultural Science 149 (2011). - ISSN 0021-8596 - p. 427 - 435.
atmospheric carbon-dioxide - elevated co2 - west-africa - intensification sri - germination ecology - lowland conditions - striga-asiatica - oryza-sativa - upland rice - plants
Global changes including increases in temperature, atmospheric greenhouse gases, soil degradation and competition for land and water resources, will have multiple impacts on rice production systems in Africa. These changes will affect weed communities, and management approaches must be adapted to take this into account. Higher temperatures and limited water availability will generally advantage C4 over C3 plants (e.g. rice). Conversely, elevated carbon dioxide (CO2) levels will improve the competitiveness of rice relative to C4 weeds, which comprise many of the problem weeds of rice. Increased atmospheric CO2 levels may also improve tolerance of rice against parasitic weeds, while prevalence of parasitic species may be amplified by soil degradation and more frequent droughts or floods. Elevated CO2 levels tend to promote growth below-ground relative to above-ground, particularly in perennial (C3) species. This may render mechanical control of weeds within a cropping season less effective or even counterproductive. Increased CO2 levels, rainfall and temperature may also reduce the effectiveness of chemical control, while the implementation of adaptation technologies, such as water-saving irrigation regimes, will have negative consequences for rice–weed competition. Rain-fed production systems are prevalent throughout Africa and these are likely to be most vulnerable to direct effects of climate change (e.g. higher temperatures and changes in rainfall patterns). Effective weed management strategies in these environments could encompass off-season tillage, the use of well-adapted cultivars (i.e. those with drought and heat tolerance, high weed competitiveness and parasitic weed resistance or tolerance) and rotations, intercropping or short, off-season fallows with weed-suppressive legumes including those that suppress parasitic weeds. In irrigated, non-flooded rice systems, weeds are expected to become more serious. Specifically, perennial rhizomatous C3 weeds and species adapted to hydromorphic conditions are expected to increase in prevalence. By implementing an integrated weed management strategy primarily targeted at weed prevention, dependency on flood water, herbicides and mechanical control can be lessened. Off-season deep tillage, stale seed bed techniques, use of clean seeds and irrigation water, competitive cultivars, timely transplanting at optimum spacing and judicious fertilizer timings are suitable candidate components for such a strategy. Integrated, novel approaches must be developed to assist farmers in coping with the challenges of weed control in the future
Next generation of elevated [CO2] experiments with crops: a critical investment for feeding the future world
Ainsworth, E.A. ; Beier, C. ; Calfapietra, C. ; Ceulemans, R. ; Durand-Tardif, M. ; Koornneef, M. - \ 2008
Plant, Cell & Environment 31 (2008)9. - ISSN 0140-7791 - p. 1317 - 1324.
atmospheric carbon-dioxide - open-air elevation - climate-change - stomatal conductance - enrichment system - photosynthesis - responses - yield - growth - face
A rising global population and demand for protein-rich diets are increasing pressure to maximize agricultural productivity. Rising atmospheric [CO2] is altering global temperature and precipitation patterns, which challenges agricultural productivity. While rising [CO2] provides a unique opportunity to increase the productivity of C3 crops, average yield stimulation observed to date is well below potential gains. Thus, there is room for improving productivity. However, only a fraction of available germplasm of crops has been tested for CO2 responsiveness. Yield is a complex phenotypic trait determined by the interactions of a genotype with the environment. Selection of promising genotypes and characterization of response mechanisms will only be effective if crop improvement and systems biology approaches are closely linked to production environments, that is, on the farm within major growing regions. Free air CO2 enrichment (FACE) experiments can provide the platform upon which to conduct genetic screening and elucidate the inheritance and mechanisms that underlie genotypic differences in productivity under elevated [CO2]. We propose a new generation of large-scale, low-cost per unit area FACE experiments to identify the most CO2-responsive genotypes and provide starting lines for future breeding programmes. This is necessary if we are to realize the potential for yield gains in the future.
Fine roots and ectomycorrhizas as indicators of environmental change.
Cudlin, P. ; Kieliszewska-Rokicka, B. ; Rudawska, M. ; Grebenc, T. ; Alberton, O. ; Lehto, T. ; Bakker, M.R. ; Borja, I. ; Konopka, B. ; Leski, T. ; Kraigher, H. ; Kuyper, T.W. - \ 2007
Plant Biosystems 141 (2007)3. - ISSN 1126-3504 - p. 406 - 425.
spruce picea-abies - pine pinus-sylvestris - experimental nitrogen addition - atmospheric carbon-dioxide - air ozone fumigation - sitchensis bong carr - norway spruce - scots pine - fagus-sylvatica - fungal communities
Human-induced and natural stress factors can affect fine roots and ectomycorrhizas. Therefore they have potential utility as indicators of environmental change. We evaluated, through meta-analysis, the magnitude of the effects of acidic deposition, nitrogen deposition, increased ozone levels, elevated atmospheric carbon dioxide, and drought on fine roots and ectomycorrhizal (ECM) characteristics. Ectomycorrhizal colonization was an unsuitable parameter for environmental change, but fine root length and biomass could be useful. Acidic deposition had a significantly negative impact on fine roots, root length being more sensitive than root biomass. There were no significant effects of nitrogen deposition or elevated tropospheric ozone on the quantitative root parameters. Elevated CO2 had a significant positive effect. Drought had a significantly negative effect on fine root biomass. The negative effect of acidic deposition and the positive effect of elevated CO2 increased over time, indicating that effects were persistent contrary the other factors. The meta-analysis also showed that experimental conditions, including both laboratory and field experiments, were a major source of variation. In addition to quantitative changes, environmental changes affect the species composition of the ectomycorrhizal fungal community.
Competition for nitrogen between Pinus sylvestris and ectomycorrhizal fungi generates potential for negative feedback under elevated CO2
Alberton, O. ; Kuyper, T.W. ; Gorissen, A. - \ 2007
Plant and Soil 296 (2007)1-2. - ISSN 0032-079X - p. 159 - 172.
atmospheric carbon-dioxide - progressive n limitation - douglas-fir seedlings - mycorrhizal fungi - mycocentric approach - growth-response - plant-response - soil biota - allocation - ecosystems
We investigated fungal species-specific responses of ectomycorrhizal (ECM) Scots pine (Pinus sylvestris) seedlings on growth and nutrient acquisition together with mycelial development under ambient and elevated CO2. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor, Suillus bovinus, S. luteus, Piloderma croceum, Paxillus involutus, Boletus badius, or non-mycorrhizal, under ambient, and elevated CO2 (350 or 700 ¿l l¿1 CO2); each treatment contained six replicates. The trial lasted 156 days. During the final 28 days, the seedlings were labeled with 14CO2. We measured hyphal length, plant biomass, 14C allocation, and plant nitrogen and phosphorus concentration. Almost all parameters were significantly affected by fungal species and/or CO2. There were very few significant interactions. Elevated CO2 decreased shoot-to-root ratio, most strongly so in species with the largest extraradical mycelium. Under elevated CO2, ECM root growth increased significantly more than hyphal growth. Extraradical hyphal length was significantly negatively correlated with shoot biomass, shoot N content, and total plant N uptake. Root dry weight was significantly negatively correlated with root N and P concentration. Fungal sink strength for N strongly affected plant growth through N immobilization. Mycorrhizal fungal-induced progressive nitrogen limitation (PNL) has the potential to generate negative feedback with plant growth under elevated CO2.
Increases in nitrogen uptake rather than nitrogen-use efficiency support higher rates of temperate forest productivity under elevated CO2
Finzi, A.C. ; Norby, R.J. ; Calfapietra, C. ; Gallet-Budynek, A. ; Gielen, B. ; Holmes, W.E. ; Hoosbeek, M.R. ; Iversen, C.M. ; Jackson, R.B. ; Kubiske, M.E. ; Ledford, J. ; Liberloo, M. ; Oren, R. ; Polle, A. ; Pritchard, S. ; Zak, D.R. ; Schlesinger, W.H. ; Ceulemans, R. - \ 2007
Proceedings of the National Academy of Sciences of the United States of America 104 (2007)35. - ISSN 0027-8424 - p. 14014 - 14019.
atmospheric carbon-dioxide - rotation poplar plantation - fine-root production - soil-n availability - enrichment face - populus-tremuloides - deciduous forest - organic nitrogen - community composition - ecosystem responses
Forest ecosystems are important sinks for rising concentrations of atmospheric CO2. In previous research, we showed that net primary production (NPP) increased by 23 ± 2% when four experimental forests were grown under atmospheric concentrations of CO2 predicted for the latter half of this century. Because nitrogen (N) availability commonly limits forest productivity, some combination of increased N uptake from the soil and more efficient use of the N already assimilated by trees is necessary to sustain the high rates of forest NPP under free-air CO2 enrichment (FACE). In this study, experimental evidence demonstrates that the uptake of N increased under elevated CO2 at the Rhinelander, Duke, and Oak Ridge National Laboratory FACE sites, yet fertilization studies at the Duke and Oak Ridge National Laboratory FACE sites showed that tree growth and forest NPP were strongly limited by N availability. By contrast, nitrogen-use efficiency increased under elevated CO2 at the POP-EUROFACE site, where fertilization studies showed that N was not limiting to tree growth. Some combination of increasing fine root production, increased rates of soil organic matter decomposition, and increased allocation of carbon (C) to mycorrhizal fungi is likely to account for greater N uptake under elevated CO2. Regardless of the specific mechanism, this analysis shows that the larger quantities of C entering the below-ground system under elevated CO2 result in greater N uptake, even in N-limited ecosystems. Biogeochemical models must be reformulated to allow C transfers below ground that result in additional N uptake under elevated CO2.
Interactions between plant growth and soil nutrient cycling under elevated CO2: a meta-analysis
Graaff, M.A. de; Groenigen, K.J. van; Six, J. ; Hungate, B. ; Kessel, C. van - \ 2006
Global Change Biology 12 (2006)11. - ISSN 1354-1013 - p. 2077 - 2091.
atmospheric carbon-dioxide - nitrogen-fixation - organic-matter - microbial biomass - tallgrass prairie - responses - enrichment - dynamics - forest - respiration
free air carbon dioxide enrichment (FACE) and open top chamber (OTC) studies are valuable tools for evaluating the impact of elevated atmospheric CO2 on nutrient cycling in terrestrial ecosystems. Using meta-analytic techniques, we summarized the results of 117 studies on plant biomass production, soil organic matter dynamics and biological N-2 fixation in FACE and OTC experiments. The objective of the analysis was to determine whether elevated CO2 alters nutrient cycling between plants and soil and if so, what the implications are for soil carbon (C) sequestration. Elevated CO2 stimulated gross N immobilization by 22%, whereas gross and net N mineralization rates remained unaffected. In addition, the soil C : N ratio and microbial N contents increased under elevated CO2 by 3.8% and 5.8%, respectively. Microbial C contents and soil respiration increased by 7.1% and 17.7%, respectively. Despite the stimulation of microbial activity, soil C input still caused soil C contents to increase by 1.2% yr(-1). Namely, elevated CO2 stimulated overall above- and belowground plant biomass by 21.5% and 28.3%, respectively, thereby outweighing the increase in CO2 respiration. In addition, when comparing experiments under both low and high N availability, soil C contents (+2.2% yr(-1)) and above- and belowground plant growth (+20.1% and+33.7%) only increased under elevated CO2 in experiments receiving the high N treatments. Under low N availability, above- and belowground plant growth increased by only 8.8% and 14.6%, and soil C contents did not increase. Nitrogen fixation was stimulated by elevated CO2 only when additional nutrients were supplied. These results suggest that the main driver of soil C sequestration is soil C input through plant growth, which is strongly controlled by nutrient availability. In unfertilized ecosystems, microbial N immobilization enhances acclimation of plant growth to elevated CO2 in the long-term. Therefore, increased soil C input and soil C sequestration under elevated CO2 can only be sustained in the long-term when additional nutrients are supplied.
Taking mycocentrism seriously: mycorrhizal fungal and plant responses to elevated CO2
Alberton, O. ; Kuyper, T.W. ; Gorissen, A. - \ 2005
New Phytologist 167 (2005)3. - ISSN 0028-646X - p. 859 - 868.
atmospheric carbon-dioxide - juvenile ponderosa pine - beech-spruce ecosystems - scots pine - nitrogen-fertilization - arbuscular mycorrhizas - trifolium-repens - growth-response - betula-pendula - soil biota
The aim here was to separately assess mycorrhizal fungal and plant responses under elevated atmospheric CO2, and to test a mycocentric model that assumes that increased carbon availability to the fungus will not automatically feed back to enhanced plant growth performance. Meta-analyses were applied across independent studies. Responses were compared in ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi, and ECM and AM plants. Responses of both mycorrhizal fungi and mycorrhizal plants to elevated CO2 were significantly positive. The response ratio for ECM fungi was 1.34 (an increase of 34%) and for AM fungi 1.21 (21%), indicating a significantly different response. The response ratio for ECM plants was 1.26, similar to that of AM plants (1.25). Fractional colonization proved to be an unsuitable fungal parameter. Evidence was found for the mycocentric view in ECM, but not in AM systems. Fungal identity and plant identity were important parameters that affected response ratios. The need for better descriptors of fungal and plant responses is emphasized
Decomposition of 14C-labeled roots in a pasture soil exposed to 10 years of elevated CO2
Groenigen, C.J. van; Gorissen, A. ; Six, J. ; Harris, D. ; Kuikman, P.J. ; Groenigen, J.W. van; Kessel, C. van - \ 2005
Soil Biology and Biochemistry 37 (2005)3. - ISSN 0038-0717 - p. 497 - 506.
atmospheric carbon-dioxide - organic-matter dynamics - trifolium-repens l - microbial biomass - lolium-perenne - forest soils - tallgrass prairie - litter quality - fine roots - turnover
The net flux of soil C is determined by the balance between soil C input and microbial decomposition, both of which might be altered under prolonged elevated atmospheric CO2. In this study, we determined the effect of elevated CO2 on decomposition of grass root material (Lolium perenne L.). 14C-labeled root material, produced under ambient (35 Pa pCO2) or elevated CO2 (70 Pa pCO2) was incubated in soil for 64 days. The soils were taken from a pasture ecosystem which had been exposed to ambient (35 Pa pCO2) or elevated CO2 (60 Pa pCO2) under FACE-conditions for 10 years and two fertilizer N rates: 140 and 560 kg N ha¿1 year¿1. In soil exposed to elevated CO2, decomposition rates of root material grown at either ambient or elevated CO2 were always lower than in the control soil exposed to ambient CO2, demonstrating a change in microbial activity. In the soil that received the high rate of N fertilizer, decomposition of root material grown at elevated CO2 decreased by approximately 17% after incubation for 64 days compared to root material grown at ambient CO2. The amount of 14CO2 respired per amount of 14C incorporated in the microbial biomass (q14CO2) was significantly lower when roots were grown under high CO2 compared to roots grown under low CO2. We hypothesize that this decrease is the result of a shift in the microbial community, causing an increase in metabolic efficiency. Soils exposed to elevated CO2 tended to respire more native SOC, both with and without the addition of the root material, probably resulting from a higher C supply to the soil during the 10 years of treatment with elevated CO2. The results show the importance of using soils adapted to elevated CO2 in studies of decomposition of roots grown under elevated CO2. Our results further suggest that negative priming effects may obscure CO2 data in incubation experiments with unlabeled substrates. From the results obtained, we conclude that a slower turnover of root material grown in an `elevated-CO2 world¿ may result in a limited net increase in C storage in ryegrass swards.
Effects of elevated CO2 and N deposition on CH4 emissions from European mires
Silvola, J. ; Saarnio, S. ; Foot, J. ; Sundh, I. ; Greenup, A. ; Heijmans, M.M.P.D. ; Ekberg, A. ; Mitchell, E.P. ; Breemen, N. van - \ 2003
Global Biogeochemical Cycles 17 (2003)2 - 1068. - ISSN 0886-6236 - p. 37 - 1-37-12.
atmospheric carbon-dioxide - methane emissions - boreal mire - raised co2 - northern peatlands - water-table - nitrogen deposition - bog vegetation - forest soils - temperature
 Methane fluxes were measured at five sites representing oligotrophic peatlands along a European transect. Five study plots were subjected to elevated CO2 concentration (560 ppm), and five plots to NH4NO3 (3 or 5 g N yr(-1)). The CH4 emissions from the control plots correlated in most cases with the soil temperatures. The depth of the water table, the pH, and the DOC, N and SO4 concentrations were only weakly correlated with the CH4 emissions. The elevated CO2 treatment gave nonsignificantly higher CH4 emissions at three sites and lower at two sites. The N treatment resulted in higher methane emissions at three sites (nonsignificant). At one site, the CH4 fluxes of the N-treatment plots were significantly lower than those of the control plots. These results were not in agreement with our hypotheses, nor with the results obtained in some earlier studies. However, the results are consistent with the results of the vegetation analyses, which showed no significant treatment effects on species relationships or biomass production.
Modelling kinetics of plant canopy architecture: concepts and applications
Birch, C.J. ; Andrieu, B. ; Fournier, C. ; Vos, J. ; Room, P. - \ 2003
European Journal of Agronomy 19 (2003). - ISSN 1161-0301 - p. 519 - 533.
maize zea-mays - atmospheric carbon-dioxide - root-system architecture - leaf-area - hydraulic architecture - vegetation canopies - radiative-transfer - climate change - grain-sorghum - epic model
Most crop models simulate the crop canopy as an homogeneous medium. This approach enables modelling of mass and energy transfer through relatively simple equations, and is useful for understanding crop production. However, schematisation of an homogeneous medium cannot address the heterogeneous nature of canopies and interactions between plants or plant organs, and errors in calculation of light interception may occur. Moreover, conventional crop models do not describe plant organs before they are visible externally e.g. young leaves of grasses. The conditions during early growth of individual organs are important determinants of final organ size, causing difficulties in incorporating effects of environmental stresses in such models. Limited accuracy in describing temporal source-sink relationships also contributes to difficulty in modelling dry matter distribution and paramaterisation of harvest indices. Functional-architectural modelling aims to overcome these limitations by (i) representing crops as populations of individual plants specified in three dimensions and (ii) by modelling whole plant growth and development from the behaviour of individual organs, based on models of organs such as leaves and internodes. Since individual plants consist of numerous organs, generic models of organ growth applicable across species are desirable. Consequently, we are studying the development of individual organs, and pararneterising it in terms of environmental variables and plant characteristics. Models incorporating plant architecture are currently applied in education, using dynamic visual representation for teaching growth and development. In research, the 3D representation of plants addresses issues presented above and new applications including modelling of pesticide distribution, fungal spore dispersal through splashing and plant to plant heterogeneity. (C) 2003 Elsevier Science B.V. All rights reserved.