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"Miscanthus"
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Influence of light and nitrogen on the photosynthetic efficiency in the C sub(4) plant Miscanthus giganteu s
There are numerous studies describing how growth conditions influence the efficiency of C sub(4) photosynthesis. However, it remains unclear how changes in the biochemical capacity versus leaf anatomy drives this acclimation. Therefore, the aim of this study was to determine how growth light and nitrogen availability influence leaf anatomy, biochemistry and the efficiency of the CO sub(2) concentrating mechanism in Miscanthus giganteu s. There was an increase in the mesophyll cell wall surface area but not cell well thickness in the high-light (HL) compared to the low-light (LL) grown plants suggesting a higher mesophyll conductance in the HL plants, which also had greater photosynthetic capacity. Additionally, the HL plants had greater surface area and thickness of bundle-sheath cell walls compared to LL plants, suggesting limited differences in bundle-sheath CO sub(2) conductance because the increased area was offset by thicker cell walls. The gas exchange estimates of phosphoenolpyruvate carboxylase (PEPc) activity were significantly less than the in vitro PEPc activity, suggesting limited substrate availability in the leaf due to low mesophyll CO sub(2) conductance. Finally, leakiness was similar across all growth conditions and generally did not change under the different measurement light conditions. However, differences in the stable isotope composition of leaf material did not correlate with leakiness indicating that dry matter isotope measurements are not a good proxy for leakiness. Taken together, these data suggest that the CO sub(2) concentrating mechanism in Miscanthus is robust under low-light and limited nitrogen growth conditions, and that the observed changes in leaf anatomy and biochemistry likely help to maintain this efficiency.
Journal Article
Catalytic gasification of biomass (Miscanthus) enhanced by CO sub(2) sorption
The main objective of this work concerns the coupling of biomass gasification reaction and CO sub(2) sorption. The study shows the feasibility to promote biomass steam gasification in a dense fluidized bed reactor with CO sub(2) sorption to enhance tar removal and hydrogen production. It also proves the efficiency of CaO-Ca sub(12)Al sub(14)O sub(33)/olivine bi-functional materials to reduce heavy tar production. Experiments have been carried out in a fluidized bed gasifier using steam as the fluidizing medium to improve hydrogen production. Bed materials consisting of CaO-based oxide for CO sub(2) sorption (CaO-Ca sub(12)Al sub(14)O sub(33)) deposited on olivine for tar reduction were synthesized, their structural and textural properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and temperature-programmed reduction (TPR) methods, and the determination of their sorption capacity and stability analyzed by thermogravimetric analysis (TGA). It appears that this CaO-Ca sub(12)Al sub(14)O sub(33)/olivine sorbent/catalyst presents a good CO sub(2) sorption stability (for seven cycles of carbonation/decarbonation). Compared to olivine and Fe/olivine in a fixed bed reactor for steam reforming of toluene chosen as tar model compound, it shows a better hydrogen production rate and a lower CO sub(2) selectivity due to its sorption on the CaO phase. In the biomass steam gasification, the use of CaO-Ca sub(12)Al sub(14)O sub(33)/olivine as bed material at 700 degree C leads to a higher H sub(2) production than olivine at 800 degree C thanks to CO sub(2) sorption. Similar tar concentration and lighter tar production (analyzed by HPLC/UV) are observed. At 700 degree C, sorbent addition allows to halve tar content and to eliminate the heaviest tars.
Journal Article
Partitioning of ecosystem respiration of CO sub(2) released during land-use transition from temperate agricultural grassland to Miscanthus giganteus
Conversion of large areas of agricultural grassland is inevitable if European and UK domestic production of biomass is to play a significant role in meeting demand. Understanding the impact of these land-use changes on soil carbon cycling and stocks depends on accurate predictions from well-parameterized models. Key considerations are cultivation disturbance and the effect of autotrophic root input stimulation on soil carbon decomposition under novel biomass crops. This study presents partitioned parameters from the conversion of semi-improved grassland to Miscanthus bioenergy production and compares the contribution of autotrophic and heterotrophic respiration to overall ecosystem respiration of CO sub(2) in the first and second years of establishment. Repeated measures of respiration from within and without root exclusion collars were used to produce time-series model integrations separating live root inputs from decomposition of grass residues ploughed in with cultivation of the new crop. These parameters were then compared to total ecosystem respiration derived from eddy covariance sensors. Average soil surface respiration was 13.4% higher in the second growing season, increasing from 2.9 to 3.29 g CO sub(2)-C m super(-2) day super(-1). Total ecosystem respiration followed a similar trend, increasing from 4.07 to 5.4 g CO sub(2)-C m super(-2) day super(-1). Heterotrophic respiration from the root exclusion collars was 32.2% lower in the second growing season at 1.20 g CO sub(2)-C m super(-2) day super(-1) compared to the previous year at 1.77 g CO sub(2)-C m super(-2) day super(-1). Of the total respiration flux over the two-year time period, aboveground autotrophic respiration plus litter decomposition contributed 38.46% to total ecosystem respiration while belowground autotrophic respiration and stimulation by live root inputs contributed 46.44% to soil surface respiration. This figure is notably higher than mean figures for nonforest soils derived from the literature and demonstrates the importance of crop-specific parameterization of respiration models.
Journal Article
The impact of soil salinity on the yield, composition and physiology of the bioenergy grass Miscanthus giganteu s
High salinity land may provide an alternative resource for the cultivation of dedicated biomass crops for renewable energy and chemicals, thus avoiding competition for land use with food crops. The commercial perennial grass Miscanthus giganteu s is a leading biomass crop; however, its response to salt stress is largely unknown. Miscanthus giganteu s was grown in pots irrigated with nine different NaCl concentrations (0, 2.86, 5.44, 7.96, 10.65, 14.68, 17.5, 19.97 and 22.4 dS m super(-1)). Biomass yield was reduced by 50% at 10.65 dS m super(-1) NaCl. Root dry matter inhibition occurred at the highest salt concentration tested, while rhizome dry weight and the ratios of root/rhizome and below-/above-ground dry matter were not affected by elevated salinity. The accumulative effect of increasing salinity reduced stem height and elongation, while photosynthesis was reduced to a smaller extent. The duration and strength of salinity exacerbated the reduction. Water use efficiency (WUE) was maintained except at the highest salinity and plants maintained stomatal conductance (g sub(s)) and leaf water content at low to moderate salinity. Miscanthus giganteu s showed strong induction of the osmoprotectant, proline and no significant increase in malondialdehyde content under increasing salinity. The ash content in leaves, increased, reducing the biomass quality at high salinity concentrations. The effects of salinity on the yield and the availability of land area in European geographical area for agriculture were investigated. Understanding the potential for growth of the C4 biomass crop Miscanthus on underutilized or abandoned land may offer a new range of targets for improved economics, crop management and breeding.
Journal Article
An interyear comparison of CO sub(2) flux and carbon budget at a commercial-scale land-use transition from semi-improved grassland to Miscanthus x giganteus
A 6-ha field at Aberystwyth, UK, was converted in 2012 from semi-improved grassland to Miscanthus x giganteus for biomass production; results from transition to the end of the first 3 years are presented here. An eddy covariance sensor mast was established from year one with a second mast added from year two, improving coverage and providing replicated measurements of CO sub(2) exchange between the ecosystem and atmosphere. Using a simple mass balance approach, above-ground and below-ground biomass production are combined with partitioned CO sub(2) fluxes to estimate short-term carbon deltas across individual years. Years one and two both ended with the site as a net source of carbon following cultivation disturbances, cumulative NEE by the end of year two was 138.57 plus or minus 16.91 g C m super(-2). The site became a cumulative net sink for carbon by the end of June in the third growing season and remained so for the rest of that year; NEE by the end of year three was -616.52 plus or minus 39.39 g C m super(-2). Carbon gains were primarily found in biomass pools, and SOC losses were limited to years one (-1.43 Mg C ha super(-1 )yr super(-1)) and two (-3.75 Mg C ha super(-1) yr super(-1)). Year three saw recoupment of soil carbon at 0.74 Mg C ha super(-1) yr super(-1) with a further estimate of 0.78 Mg C ha super(-1) incorporated through litter inputs over the 3 years, suggesting a net loss of SOC at 3.7 Mg ha super(-1) from a 0- to 30-cm baseline of 78.61 plus or minus 3.28 Mg ha super(-1), down 4.7%. Assuming this sequestration rate as a minimum would suggest replacement of cultivation losses of SOC by year 8 of a potential 15- to 20-year crop. Potential coal replacement per hectare of harvest over the three-year study would offset 6-8 Mg of carbon emission, more than double the SOC losses.
Journal Article
Can miscanthus C sub(4) photosynthesis compete with festulolium C sub(3) photosynthesis in a temperate climate?
Miscanthus, a perennial grass with C sub(4) photosynthesis, is regarded as a promising energy crop due to its high biomass productivity. Compared with other C sub(4) species, most miscanthus genotypes have high cold tolerances at 14 degree C. However, in temperate climates, temperatures below 14 degree C are common and our aim was to elucidate cold tolerances of different miscanthus genotypes and compare with a C sub(3) perennial grass - festulolium. Eleven genotypes of M. sacchariflorus, M. sinensis, M. tinctorius, M. giganteus as well as festulolium were grown under warm (24/20 degree C, day/night) and three under cold (14/10 degree C, 10/8 degree C and 6/4 degree C) conditions in a controlled environment. Measurements of photosynthetic light response curves, operating quantum yield of photosystem II ( Phi PSII), net photosynthetic rate at a PAR of 1000 mu mol m super(-2) s super(-1) (A sub(1000)) and dark-adapted chlorophyll fluorescence (Fv/Fm) were made at each temperature. In addition, temperature response curves were measured after the plants had been grown at 6/4 degree C. The results showed that two tetraploid M. sacchariflorus and the standard triploid M. giganteus cv. Hornum retained a significantly higher photosynthetic capacity than other miscanthus genotypes at each temperature level and still maintained photosynthesis after growing for a longer period at 6/4 degree C. Only two of five measured miscanthus genotypes increased photosynthesis immediately after the temperature was raised again. The photosynthetic capacity of festulolium was significantly higher at 10/8 degree C and 6/4 degree C than of miscanthus genotypes. This indicates that festulolium may be more productive than the currently investigated miscanthus genotypes in cool, maritime climates. Within miscanthus, only one M. sacchariflorus genotype exhibited the same photosynthetic capacity as Hornum at both cold conditions and when the temperature was raised again. Therefore, this genotype could be useful for breeding new varieties with an improved cold tolerance vis-a-vis Hornum, and be valuable in broadening the genetic diversity of miscanthus for more widespread cultivation in temperate climates.
Journal Article
Can chilling tolerance of C sub(4) photosynthesis in Miscanthus be transferred to sugarcane?
The goal of this study was to investigate whether chilling tolerance of C sub(4) photosynthesis in Miscanthus can be transferred to sugarcane by hybridization. Net leaf CO sub(2) uptake (A sub(sat)) and the maximum operating efficiency of photosystem II ([ETH][curren] sub(PSII)) were measured in warm conditions (25 degree C/20 degree C), and then during and following a chilling treatment of 10 degree C/5 degree C for 11 day in controlled environment chambers. Two of three hybrids (miscanes), 'US 84-1058' and 'US 87-1019', did not differ significantly from the chilling tolerant M. giganteus 'Illinois' (Mxg), for A sub(sat), and Phi sub(PSII) measured during chilling. For Mxg grown at 10 degree C/5 degree C for 11 days, A sub(sat) was 4.4 mu mol m super(-2) s super(-1), while for miscane 'US 84-1058' and 'US 87-1019', A sub(sat) was 5.7 and 3.5 mu mol m super(-2) s super(-1), respectively. Miscanes 'US 84-1058' and 'US 87-1019' and Mxg had significantly higher rates of A sub(sat) during chilling than three tested sugarcanes. A third miscane showed lower rates than Mxg during chilling, but recovered to higher rates than sugarcane upon return to warm conditions. Chilling tolerance of 'US 84-1058' was further confirmed under autumn field conditions in southern Illinois. The selected chilling tolerant miscanes have particular value for biomass feedstock and biofuel production and at the same time they can be a starting point for extending sugarcane's range to colder climates.
Journal Article
Changes in isotopic signatures of soil carbon and CO sub(2) respiration immediately and one year after Miscanthus removal
The removal of perennial bioenergy crops, such as Miscanthus, has rarely been studied although it is an important form of land use change. Miscanthus is a C4 plant, and the carbon (C) it deposits during its growth has a different isotopic signature ( super(12)/ super(13)C) compared to a C3 plant. Identifying the proportion of C stored and released to the atmosphere is important information for ecosystem models and life cycle analyses. During a removal experiment in June 2011 of a 20-year old Miscanthus field (Grignon, France), vegetation was removed mechanically and chemically. Two replicate plots were converted into a rotation of annual crops, two plots had Miscanthus removed with no soil disturbance, followed by bare soil (set-aside), one control plot was left with continued Miscanthus cultivation, and an adjacent field was used as annual arable crops control. There was a significant difference in the isotopic composition of the total soil C under Miscanthus compared with adjacent annual arable crops in all three measured soil layers (0-5, 5-10 and 10-20 cm). Before Miscanthus removal, total C in the soil under Miscanthus ranged from 4.9% in the top layer to 3.9% in the lower layers with delta super(13)C values of -16.3 to -17.8 while soil C under the adjacent arable crop was significantly lower and ranged from 1.6 to 2% with delta super(13)C values of -23.2. This did not change much in 2012, suggesting the accumulation of soil C under Miscanthus persists for at least the first year. In contrast, the isotopic signals of soil respiration 1 year after Miscanthus removal from recultivated and set-aside plots were similar to that of the annual arable control, while just after removal the signals were similar to that of the Miscanthus control. This suggests a rapid change in the form of soil C pools that are respired.
Journal Article
Analysis of young Miscanthus giganteu s yield variability: a survey of farmers' fields in east central France
Miscanthus giganteus is often regarded as one of the most promising crops to produce bioenergy because it is renowned for its high biomass yields, combined with low input requirements. However, its productivity has been mainly studied in experimental conditions. Our study aimed at characterizing and explaining young M. giganteus yield variability on a farmers' field network located in the supply area of a cooperative society in east central France. It included the first three growth years of the crop. We defined and calculated a set of indicators of limiting factors that could be involved in yield variations and used the mixed-model method to identify those explaining most of the yield variation. Commercial yields averaged 8.1 and 12.8 t DM ha super(-1) for the second and third growth year, respectively. However, these mean results concealed a high variability, ranging from 3 to 19 t DM ha super(-1) . Commercial yields, measured on whole fields, were on average 20% lower than plot yields, measured on a small area (two plots of 25 m super(2)). Yields were found to be much more related to shoot density than to shoot mass, and particularly to the shoot density established at the end of the planting year. We highlighted that planting success was decisive and was built during the whole plantation year. Fields with the lowest yields also had the highest weed cover, which was influenced by the distance between the field and the farmhouse, the preceding crop and the soil type. Our findings show that growing young M. giganteus on farmers' fields involves limiting factors different from those commonly reported in the literature for experimental conditions and they could be useful to assess the economic and environmental impacts of growing M. giganteus on farmers' fields. They could also stimulate the discussion about growing bioenergy crops on marginal lands.
Journal Article