A new compartmentalised rhizotron system for root phenotyping

Although roots are the key organs for plant fitness, studies on root phenotyping and dynamics of water uptake are difficult and costly. Here we present a new compartimentalised rhizotron system that attempts to integrate some positive features of conventional methods for assessing root patterns at field and laboratory scale. The system has a petrolatum/paraffin hydrophobic film, which allows the com-partmentalisation of soil layers along the cylinder profile, thus roots and soil moisture content are split into completely independent segments. In this preliminary study, we tested the system by creating a top-bottom split root arrangement that mimic the fluctuating levels of a water table to determine the dynamic interrelationship of canopy water conservation and root water acquisition from both shallow and deep roots of giant reed. Thanks to its versatility, the system enabled us to perform a root phenotyping study within distinct and independent soil portions

The effects of integrated food and bioenergy cropping systems on crop yields, soil health, and biomass quality: The EU and Brazilian experience

Integrated food and bioenergy production is a promising way to ensure regional/national food and energy security, efficient use of soil resources, and enhanced biodiversity, while contributing to the abatement of CO2 emissions. The objective of this study was to assess alternative crop rotation schemes as the basis for integrating and enhancing the sustainable biomass production within the food-energy agricultural context. Sunn hemp (Crotalaria spp.) in rotation with wheat (Triticum spp.) in the EU and with sugarcane (Saccharum spp.) in Brazil were evaluated. Sunn hemp did not negatively affect crop's productivity and soil fertility; wheat grain yields were maintained around the mean regional production levels (6, 7, 3 and Mg ha(-1) in Greece, Italy, and Spain, respectively), and the cumulative biomass in the extended rotation (wheat straw+sunn hemp) was between 1.5 and 2.0 times higher than in the conventional rotation. In Brazil, sugarcane stalks yield in clay soils increased by around 15 Mg ha(-1) year(-1) under sunn hemp rotation in comparison with bare fallow. Moreover, sunn hemp in the EU rotations did not have negative effects on soil available macronutrients, organic matter, pH, and cation exchange capacity, neither on C and N stocks in Brazil. The qualitative characteristics (mineral, ash, and hemicelluloses contents) of the cumulated biomass were somehow higher (in average +26%, +35%, and +3.4%, respectively) than in the conventional system. In summary, in temperate and tropical climates the integration of dedicated biomass legume crops within conventional systems could lead to enhanced biomass availability, crop diversification, and efficient use (in space and time) of the land resources

Transcriptional and Physiological Analyses to Assess the Effects of a Novel Biostimulant in Tomato

: This work aimed to study the effects in tomato (Solanum lycopersicum L.) of foliar applications of a novel calcium-based biostimulant (SOB01) using an omics approach involving transcriptomics and physiological profiling. A calcium-chloride fertilizer (SOB02) was used as a product reference standard. Plants were grown under well-watered (WW) and water stress (WS) conditions in a growth chamber. We firstly compared the transcriptome profile of treated and untreated tomato plants using the software RStudio. Totally, 968 and 1,657 differentially expressed genes (DEGs) (adj-p-value < 0.1 and |log2(fold change)| ≥ 1) were identified after SOB01 and SOB02 leaf treatments, respectively. Expression patterns of 9 DEGs involved in nutrient metabolism and osmotic stress tolerance were validated by real-time quantitative reverse transcription PCR (RT-qPCR) analysis. Principal component analysis (PCA) on RT-qPCR results highlighted that the gene expression profiles after SOB01 treatment in different water regimes were clustering together, suggesting that the expression pattern of the analyzed genes in well water and water stress plants was similar in the presence of SOB01 treatment. Physiological analyses demonstrated that the biostimulant application increased the photosynthetic rate and the chlorophyll content under water deficiency compared to the standard fertilizer and led to a higher yield in terms of fruit dry matter and a reduction in the number of cracked fruits. In conclusion, transcriptome and physiological profiling provided comprehensive information on the biostimulant effects highlighting that SOB01 applications improved the ability of the tomato plants to mitigate the negative effects of water stress

A dual-omics approach for profiling plant responses to biostimulant applications under controlled and field conditions

A comprehensive approach using phenomics and global transcriptomics for dissecting plant response to biostimulants is illustrated with tomato (Solanum lycopersicum cv. Micro-Tom and Rio Grande) plants cultivated in the laboratory, greenhouse, and open field conditions. Biostimulant treatment based on an Ascophyllum nodosum extract (ANE) was applied as a foliar spray with two doses (1 or 2 l ha-1) at three different phenological stages (BBCH51, BBCH61, and BBCH65) during the flowering phase. Both ANE doses resulted in greater net photosynthesis rate, stomatal conductance, and fruit yield across all culture conditions. A global transcriptomic analysis of leaves from plants grown in the climate chamber, revealed a greater number of differentially expressed genes (DEGs) with the low ANE dose compared to the greater one. The second and third applications induced broader transcriptome changes compared to the first one, indicating a cumulative treatment effect. The functional enrichment analysis of DEGs highlighted pathways related to stimulus-response and photosynthesis, consistent with the morpho-physiological observations. This study is the first comprehensive dual-omics approach for profiling plant responses to biostimulants across three different culture conditions

Transcriptomic and physiological approaches to decipher cold stress mitigation exerted by brown-seaweed extract application in tomato

Chilling temperatures represent a challenge for crop species originating from warm geographical areas. In this situation, biostimulants serve as an eco-friendly resource to mitigate cold stress in crops. Tomato (Solanum lycopersicum L.) is an economically important vegetable crop, but quite sensitive to cold stress, which it encounters in both open field and greenhouse settings. In this study, the biostimulant effect of a brown-seaweed extract (BSE) has been evaluated in tomato exposed to low temperature. To assess the product effects, physiological and molecular characterizations were conducted. Under cold stress conditions, stomatal conductance, net photosynthesis, and yield were significantly (p ≤ 0.05) higher in BSE-treated plants compared to the untreated ones. A global transcriptomic survey after BSE application revealed the impact of the BSE treatment on genes leading to key responses to cold stress. This was highlighted by the significantly enriched GO categories relative to proline (GO:0006560), flavonoids (GO:0009812, GO:0009813), and chlorophyll (GO:0015994). Molecular data were integrated by biochemical analysis showing that the BSE treatment causes greater proline, polyphenols, flavonoids, tannins, and carotenoids contents.The study highlighted the role of antioxidant molecules to enhance tomato tolerance to low temperature mediated by BSE-based biostimulant

Environmentally sustainable biogas? the key role of manure co-digestion with energy crops

We analyzed the environmental impacts of three biogas systems based on dairy manure, sorghum and maize. The geog. scope of the anal. is the Po valley, in Italy. The anaerobic digestion of manure guarantees high GHG (Green House Gases) savings thanks to the avoided emissions from the traditional storage and management of raw manure as org. fertiliser. GHG emissions for maize and sorghum-based systems, on the other hand, are similar to those of the Italian electricity mix. In crop-based systems, the plants with open-tank storage of digestate emit 50% more GHG than those with gas-tight tanks. In all the environmental impact categories analyzed (acidification, particulate matter emissions, and eutrophication), energy crops based systems have much higher impacts than the Italian electricity mix. Maize-based systems cause higher impacts than sorghum, due to more intensive cultivation. Manure-based pathways have always lower impacts than the energy crops based pathways, however, all biogas systems cause much higher impacts than the current Italian electricity mix. We conclude that manure digestion is the most efficient way to reduce GHG emissions; although there are trade-offs with other local environmental impacts. Biogas prodn. from crops; although not providing environmental benefits per se; may be regarded as an option to facilitate the deployment of manure digestion.Agostini, A.; Battini, F.; Giuntoli, J.; Tabaglio, V.; Padella, M.; Baxter, D.; Marelli, L.... (2015). Environmentally sustainable biogas? the key role of manure co-digestion with energy crops. Energies. 8(6):5234-5265. https://doi.org/10.3390/en8065234S5234526586Bacenetti, J., Fusi, A., Negri, M., Guidetti, R., & Fiala, M. (2014). Environmental assessment of two different crop systems in terms of biomethane potential production. Science of The Total Environment, 466-467, 1066-1077. doi:10.1016/j.scitotenv.2013.07.109Capponi, S., Fazio, S., & Barbanti, L. (2012). CO2 savings affect the break-even distance of feedstock supply and digestate placement in biogas production. Renewable Energy, 37(1), 45-52. doi:10.1016/j.renene.2011.05.005Gerin, P. A., Vliegen, F., & Jossart, J.-M. (2008). Energy and CO2 balance of maize and grass as energy crops for anaerobic digestion. Bioresource Technology, 99(7), 2620-2627. doi:10.1016/j.biortech.2007.04.049Battini, F., Agostini, A., Boulamanti, A. K., Giuntoli, J., & Amaducci, S. (2014). Mitigating the environmental impacts of milk production via anaerobic digestion of manure: Case study of a dairy farm in the Po Valley. Science of The Total Environment, 481, 196-208. doi:10.1016/j.scitotenv.2014.02.038Boulamanti, A. K., Donida Maglio, S., Giuntoli, J., & Agostini, A. (2013). Influence of different practices on biogas sustainability. Biomass and Bioenergy, 53, 149-161. doi:10.1016/j.biombioe.2013.02.020Blengini, G. A., Brizio, E., Cibrario, M., & Genon, G. (2011). LCA of bioenergy chains in Piedmont (Italy): A case study to support public decision makers towards sustainability. Resources, Conservation and Recycling, 57, 36-47. doi:10.1016/j.resconrec.2011.10.003González-García, S., Bacenetti, J., Negri, M., Fiala, M., & Arroja, L. (2013). Comparative environmental performance of three different annual energy crops for biogas production in Northern Italy. Journal of Cleaner Production, 43, 71-83. doi:10.1016/j.jclepro.2012.12.017Lansche, J., & Müller, J. (2012). Life cycle assessment of energy generation of biogas fed combined heat and power plants: Environmental impact of different agricultural substrates. Engineering in Life Sciences, 12(3), 313-320. doi:10.1002/elsc.201100061Lijó, L., González-García, S., Bacenetti, J., Fiala, M., Feijoo, G., Lema, J. M., & Moreira, M. T. (2014). Life Cycle Assessment of electricity production in Italy from anaerobic co-digestion of pig slurry and energy crops. Renewable Energy, 68, 625-635. doi:10.1016/j.renene.2014.03.005Lijó, L., González-García, S., Bacenetti, J., Fiala, M., Feijoo, G., & Moreira, M. T. (2014). Assuring the sustainable production of biogas from anaerobic mono-digestion. Journal of Cleaner Production, 72, 23-34. doi:10.1016/j.jclepro.2014.03.022Whiting, A., & Azapagic, A. (2014). Life cycle environmental impacts of generating electricity and heat from biogas produced by anaerobic digestion. Energy, 70, 181-193. doi:10.1016/j.energy.2014.03.103Berndes, G. (2002). Bioenergy and water—the implications of large-scale bioenergy production for water use and supply. Global Environmental Change, 12(4), 253-271. doi:10.1016/s0959-3780(02)00040-7Gheewala, S. H., Berndes, G., & Jewitt, G. (2011). The bioenergy and water nexus. 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Sweet and fibre sorghum (Sorghum bicolor (L.) Moench), energy crops in the frame of environmental protection from excessive nitrogen loads. European Journal of Agronomy, 25(1), 30-39. doi:10.1016/j.eja.2006.03.001Searchinger, T., Heimlich, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., … Yu, T.-H. (2008). Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change. Science, 319(5867), 1238-1240. doi:10.1126/science.1151861Styles, D., Gibbons, J., Williams, A. P., Stichnothe, H., Chadwick, D. R., & Healey, J. R. (2014). Cattle feed or bioenergy? Consequential life cycle assessment of biogas feedstock options on dairy farms. GCB Bioenergy, 7(5), 1034-1049. doi:10.1111/gcbb.12189PE International AGwww.pe-international.comPlevin, R. J., Delucchi, M. A., & Creutzig, F. (2013). Using Attributional Life Cycle Assessment to Estimate Climate-Change Mitigation Benefits Misleads Policy Makers. Journal of Industrial Ecology, 18(1), 73-83. doi:10.1111/jiec.12074Marañón, E., Salter, A. M., Castrillón, L., Heaven, S., & Fernández-Nava, Y. (2011). Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste. Waste Management, 31(8), 1745-1751. doi:10.1016/j.wasman.2011.03.015Chantigny, M. H., Angers, D. A., Rochette, P., Bélanger, G., Massé, D., & Côté, D. (2007). Gaseous Nitrogen Emissions and Forage Nitrogen Uptake on Soils Fertilized with Raw and Treated Swine Manure. Journal of Environment Quality, 36(6), 1864. doi:10.2134/jeq2007.0083Loria, E. R., & Sawyer, J. E. (2005). Extractable Soil Phosphorus and Inorganic Nitrogen following Application of Raw and Anaerobically Digested Swine Manure. Agronomy Journal, 97(3), 879. doi:10.2134/agronj2004.0249Möller, K., Stinner, W., Deuker, A., & Leithold, G. (2008). Effects of different manuring systems with and without biogas digestion on nitrogen cycle and crop yield in mixed organic dairy farming systems. Nutrient Cycling in Agroecosystems, 82(3), 209-232. doi:10.1007/s10705-008-9196-9Koehler, B., Diepolder, M., Ostertag, J., Thurner, S., & Spiekers, H. (2013). Dry matter losses of grass, lucerne and maize silages in bunker silos. Agricultural and Food Science, 22(1), 145-150. doi:10.23986/afsci.6715Herrmann, C., Heiermann, M., & Idler, C. (2011). Effects of ensiling, silage additives and storage period on methane formation of biogas crops. Bioresource Technology, 102(8), 5153-5161. doi:10.1016/j.biortech.2011.01.012Schittenhelm, S. (2010). Effect of Drought Stress on Yield and Quality of Maize/Sunflower and Maize/Sorghum Intercrops for Biogas Production. Journal of Agronomy and Crop Science. doi:10.1111/j.1439-037x.2010.00418.xGas Engines for CHP Units and Gensetshttp://www.truck.man.eu/man/media/content_medien/doc/global_engines/power/BR_Power_Gas_EN.pdf?_ga=1.109727301.1989443271.1432903866Walla, C., & Schneeberger, W. (2008). The optimal size for biogas plants. Biomass and Bioenergy, 32(6), 551-557. doi:10.1016/j.biombioe.2007.11.009Liebetrau, J., Clemens, J., Cuhls, C., Hafermann, C., Friehe, J., Weiland, P., & Daniel-Gromke, J. (2010). Methane emissions from biogas-producing facilities within the agricultural sector. Engineering in Life Sciences, 10(6), 595-599. doi:10.1002/elsc.201000070Li, Z., Yin, F., Li, H., Wang, X., & Lian, J. (2013). A novel test method for evaluating the methane gas permeability of biogas storage membrane. Renewable Energy, 60, 572-577. doi:10.1016/j.renene.2013.06.010Amon, B., Kryvoruchko, V., Amon, T., & Zechmeister-Boltenstern, S. (2006). Methane, nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment. Agriculture, Ecosystems & Environment, 112(2-3), 153-162. doi:10.1016/j.agee.2005.08.030Amon, B., Kryvoruchko, V., Moitzi, G., & Amon, T. (2006). Greenhouse gas and ammonia emission abatement by slurry treatment. International Congress Series, 1293, 295-298. doi:10.1016/j.ics.2006.01.069Muñoz, I., Schmidt, J. H., Brandão, M., & Weidema, B. P. (2014). Rebuttal to ‘Indirect land use change (iLUC) within life cycle assessment (LCA) - scientific robustness and consistency with international standards’. GCB Bioenergy, 7(4), 565-566. doi:10.1111/gcbb.12231Carrosio, G. (2013). Energy production from biogas in the Italian countryside: Policies and organizational models. Energy Policy, 63, 3-9. doi:10.1016/j.enpol.2013.08.072Posch, M., Seppälä, J., Hettelingh, J.-P., Johansson, M., Margni, M., & Jolliet, O. (2008). The role of atmospheric dispersion models and ecosystem sensitivity in the determination of characterisation factors for acidifying and eutrophying emissions in LCIA. The International Journal of Life Cycle Assessment, 13(6), 477-486. doi:10.1007/s11367-008-0025-9Seppälä, J., Posch, M., Johansson, M., & Hettelingh, J.-P. (2005). Country-dependent Characterisation Factors for Acidification and Terrestrial Eutrophication Based on Accumulated Exceedance as an Impact Category Indicator (14 pp). The International Journal of Life Cycle Assessment, 11(6), 403-416. doi:10.1065/lca2005.06.215The Riskpoll Softwarehttp://www.arirabl.com/softwareGreco, S. L., Wilson, A. M., Spengler, J. D., & Levy, J. I. (2007). Spatial patterns of mobile source particulate matter emissions-to-exposure relationships across the United States. Atmospheric Environment, 41(5), 1011-1025. doi:10.1016/j.atmosenv.2006.09.025Abdalla, M., Osborne, B., Lanigan, G., Forristal, D., Williams, M., Smith, P., & Jones, M. B. (2013). Conservation tillage systems: a review of its consequences for greenhouse gas emissions. Soil Use and Management, 29(2), 199-209. doi:10.1111/sum.12030Snyder, C. S., Bruulsema, T. W., Jensen, T. L., & Fixen, P. E. (2009). Review of greenhouse gas emissions from crop production systems and fertilizer management effects. Agriculture, Ecosystems & Environment, 133(3-4), 247-266. doi:10.1016/j.agee.2009.04.021Zhang, S., Li, Q., Lü, Y., Zhang, X., & Liang, W. (2013). Contributions of soil biota to C sequestration varied with aggregate fractions under different tillage systems. Soil Biology and Biochemistry, 62, 147-156. doi:10.1016/j.soilbio.2013.03.023Derpsch, R., Franzluebbers, A. J., Duiker, S. W., Reicosky, D. C., Koeller, K., Friedrich, T., … Weiss, K. (2014). Why do we need to standardize no-tillage research? Soil and Tillage Research, 137, 16-22. doi:10.1016/j.still.2013.10.002Franzluebbers, A. J. (2010). Achieving Soil Organic Carbon Sequestration with Conservation Agricultural Systems in the Southeastern United States. Soil Science Society of America Journal, 74(2), 347. doi:10.2136/sssaj2009.0079Soane, B. D., Ball, B. C., Arvidsson, J., Basch, G., Moreno, F., & Roger-Estrade, J. (2012). No-till in northern, western and south-western Europe: A review of problems and opportunities for crop production and the environment. Soil and Tillage Research, 118, 66-87. doi:10.1016/j.still.2011.10.015Mircea, M., Ciancarella, L., Briganti, G., Calori, G., Cappelletti, A., Cionni, I., … Zanini, G. (2014). Assessment of the AMS-MINNI system capabilities to simulate air quality over Italy for the calendar year 2005. Atmospheric Environment, 84, 178-188. doi:10.1016/j.atmosenv.2013.11.006Tabaglio, V., & Gavazzi, C. (2009). Monoculture Maize (Zea mays L.) Cropped Under Conventional Tillage, No-tillage and N Fertilization: (I) Three Year Yield Performances. Italian Journal of Agronomy, 4(3), 61. doi:10.4081/ija.2009.3.61Pirlo, G., & Carè, S. (2013). A Simplified Tool for Estimating Carbon Footprint of Dairy Cattle Milk. Italian Journal of Animal Science, 12(4), e81. doi:10.4081/ijas.2013.e81Sanz-Cobena, A., Sánchez-Martín, L., García-Torres, L., & Vallejo, A. (2012). Gaseous emissions of N2O and NO and NO3− leaching from urea applied with urease and nitrification inhibitors to a maize (Zea mays) crop. Agriculture, Ecosystems & Environment, 149, 64-73. doi:10.1016/j.agee.2011.12.016Stehfest, E., & Bouwman, L. (2006). N2O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions. Nutrient Cycling in Agroecosystems, 74(3), 207-228. doi:10.1007/s10705-006-9000-7Perego, A., Basile, A., Bonfante, A., De Mascellis, R., Terribile, F., Brenna, S., & Acutis, M. (2012). Nitrate leaching under maize cropping systems in Po Valley (Italy). Agriculture, Ecosystems & Environment, 147, 57-65. doi:10.1016/j.agee.2011.06.014Van der Werf, H. M. G., Kanyarushoki, C., & Corson, M. S. (2009). An operational method for the evaluation of resource use and environmental impacts of dairy farms by life cycle assessment. Journal of Environmental Management, 90(11), 3643-3652. doi:10.1016/j.jenvman.2009.07.003Álvaro-Fuentes, J., Plaza-Bonilla, D., Arrúe, J. L., Lampurlanés, J., & Cantero-Martínez, C. (2012). Soil organic carbon storage in a no-tillage chronosequence under Mediterranean conditions. Plant and Soil, 376(1-2), 31-41. doi:10.1007/s11104-012-1167-xBaker, J. M., Ochsner, T. E., Venterea, R. T., & Griffis, T. J. (2007). Tillage and soil carbon sequestration—What do we really know? Agriculture, Ecosystems & Environment, 118(1-4), 1-5. doi:10.1016/j.agee.2006.05.014Borin, M., Menini, C., & Sartori, L. (1997). Effects of tillage systems on energy and carbon balance in north-eastern Italy. Soil and Tillage Research, 40(3-4), 209-226. doi:10.1016/s0167-1987(96)01057-4De Sanctis, G., Roggero, P. P., Seddaiu, G., Orsini, R., Porter, C. H., & Jones, J. W. (2012). Long-term no tillage increased soil organic carbon content of rain-fed cereal systems in a Mediterranean area. European Journal of Agronomy, 40, 18-27. doi:10.1016/j.eja.2012.02.002Powlson, D. S., Stirling, C. M., Jat, M. L., Gerard, B. G., Palm, C. A., Sanchez, P. A., & Cassman, K. G. (2014). Limited potential of no-till agriculture for climate change mitigation. Nature Climate Change, 4(8), 678-683. doi:10.1038/nclimate229

Seasonal switchgrass ecotype contributions to soil organic carbon, deep soil microbial community composition and rhizodeposit uptake during an extreme drought

The importance of rhizodeposit C and associated microbial communities in deep soil C stabilization is relatively unknown. Phenotypic variability in plant root biomass could impact C cycling through belowground plant allocation, rooting architecture, and microbial community abundance and composition. We used a pulse-chase 13C labeling experiment with compound-specific stable-isotope probing to investigate the importance of rhizodeposit C to deep soil microbial biomass under two switchgrass ecotypes (Panicum virgatum L., Kanlow and Summer) with contrasting root morphology. We quantified root phenology, soil microbial biomass (phospholipid fatty acids, PLFA), and microbial rhizodeposit uptake (13C-PLFAs) to 150 cm over one year during a severe drought. The lowland ecotype, Kanlow, had two times more root biomass with a coarser root system compared to the upland ecotype, Summer. Over the drought, Kanlow lost 78% of its root biomass, while Summer lost only 60%. Rhizosphere microbial communities associated with both ecotypes were similar. However, rhizodeposit uptake under Kanlow had a higher relative abundance of gram-negative bacteria (44.1%), and Summer rhizodeposit uptake was primarily in saprotrophic fungi (48.5%). Both microbial community composition and rhizodeposit uptake shifted over the drought into gram-positive communities. Rhizosphere soil C was greater one year later under Kanlow due to turnover of unlabeled structural root C. Despite a much greater root biomass under Kanlow, rhizosphere δ13C was not significantly different between the two ecotypes, suggesting greater microbial C input under the finer rooted species, Summer, whose microbial associations were predominately saprotrophic fungi. Ecotype specific microbial communities can direct rhizodeposit C flow and C accrual deep in the soil profile and illustrate the importance of the microbial community in plant strategies to survive environmental stress such as drought

Land use change from C3 grassland to C4 <em>Miscanthus</em>: effects on soil carbon content and estimated mitigation benefit after six years

To date, most Miscanthus trials and commercial fields have been planted on arable land. Energy crops will need to be grown more on lower grade lands unsuitable for arable crops. Grasslands represent a major land resource for energy crops. In grasslands, where soil organic carbon (SOC) levels can be high, there have been concerns that the carbon mitigation benefits of bioenergy from Miscanthus could be offset by losses in SOC associated with land use change. At a site in Wales (UK), we quantified the relatively short-term impacts (6 years) of four novel Miscanthus hybrids and Miscanthus × giganteus on SOC in improved grassland. After 6 years, using stable carbon isotope ratios (13C/12C), the amount of Miscanthus derived C (C4) in total SOC was considerable (ca. 12%) and positively correlated to belowground biomass of different hybrids. Nevertheless, significant changes in SOC stocks (0–30 cm) were not detected as C4 Miscanthus carbon replaced the initial C3 grassland carbon; however, initial SOC decreased more in the presence of higher belowground biomass. We ascribed this apparently contradictory result to the rhizosphere priming effect triggered by easily available C sources. Observed changes in SOC partitioning were modelled using the RothC soil carbon turnover model and projected for 20 years showing that there is no significant change in SOC throughout the anticipated life of a Miscanthus crop. We interpret our observations to mean that the new labile C from Miscanthus has replaced the labile C from the grassland and, therefore, planting Miscanthus causes an insignificant change in soil organic carbon. The overall C mitigation benefit is therefore not decreased by depletion of soil C and is due to substitution of fossil fuel by the aboveground biomass, in this instance 73–108 Mg C ha−1 for the lowest and highest yielding hybrids, respectively, after 6 years

Nära till naturen : en diskussion om riktlinjer för grundtillgång på friluftsmarker nära tätorter /

This study tested a method to quantify and locate hydraulic lift (HL, defined as the passive upward water flow from wetter to dryer soil zones through the plant root system) by combining an experiment using the stable water isotope 1H218O as a tracer with a soil–plant water flow model. Our methodology consisted in (i) establishing the initial conditions for HL in a large rhizobox planted with Italian ryegrass (Lolium multiflorum Lam.), (ii) labeling water in the deepest soil layer with an 18O-enriched solution, (iii) monitoring the water O isotopic composition in soil layers to find out changes in the upper layers that would reflect redistribution of 18O-enriched water from the bottom layers by the roots, and (iv) comparing the observed soil water O isotopic composition to simulation results of a three-dimensional model of water flow and isotope transport in the soil–root system. Our main findings were that (i) the depth and strength of the observed changes in soil water O isotopic composition could be well reproduced with a modeling approach (RMSE = 0.2‰, i.e., equivalent to the precision of the isotopic measurements), (ii) the corresponding water volume involved in HL was estimated to account for 19% of the plant transpiration of the following day, i.e., 0.45 mm of water, and was in agreement with the observed soil water content changes, and (iii) the magnitude of the simulated HL was sensitive to both plant and soil hydraulic properties