Physiological and productive responses of Miscanthus genotypes to different climatic constraints in Mediterranean environment

Strong global growth and development has increased demand for energy to refine, manufacture and transport products to support the lifestyles of an increasingly developing and globalized world. In recent decades, fossil fuels have become important sources of energy. However, with increasing demand, there has been developing concern over the sustainability of fossil fuels relating to their potential future sources and harmful byproducts of use, specifically large net carbon releases, which has spurred interest towards the use of alternative renewable energy sources. Potential alternatives are available including wind, solar, hydro, and biomass, all of which are touted to have greater environmental benefits relative to fossil fuels. There has been increasing interest in the use of perennial grasses as energy crops in the US and Europe since the mid-1980s. The characteristics which make perennial grasses attractive for biomass production are their high yield potential, the high contents of lignin and cellulose of their biomass and their generally anticipated positive environmental impact. For this purpose, three different researches were carried out with the aim of studying i) the adaptation and biomass production potential of 18 Miscanthus accessions, representing 5 Miscanthus species, collected from a wide geographical range (Numata, 1974) for suitability to semi-arid Mediterranean climates; ii) the effect of harvest time (autumn and winter time) on biomass yield, morph-biometric characters, moisture content, cellulose, hemicelluloses and lignin contents for second generation bioethanol production and ash content for combustion purposes in a long term plantation of Miscanthus x giganteus in a Mediterranean environment; iii) the effect of heat stress, in controlled-environment, on 5 Miscanthus genotypes, coming from the Miscanthus germplasm collection at Institute of Biological, Environmental and Rural Sciences (IBERS) of the Aberystwyth University Wales UK, to identify if the high temperature have a negative effect on the growth, partitioning and physiology of Miscanthus plants. Results suggest that some Miscanthus accessions are suitably adapted to maintain high biomass in a semi-arid Mediterranean environment and that the most commonly available commercial Miscanthus genotypes (M. x giganteus and Goliath) are not well adapted to the Mediterranean climate or environments where water is a limiting factor, and there are other Miscanthus accessions that produce high biomass in water limited semi-arid regions. Long term Miscanthus plantations strictly depend by the thermopluviometric trend of the growing season, decreasing biomass yield as rainfall reduces and the biomass for specific end uses presents higher quality (in terms of more hemicellulose and cellulose content than ash content), with winter harvest. Relative to low temperature, high temperature decreased the plant height (~48%), above-ground dry biomass (~66%), below-ground dry biomass (~26%) and photosynthetic response to absorbed light (~13%). The most widely available and commonly used variety of Miscanthus is sensitive to high temperatures and there are other genotypes that have a higher capacity for carbon assimilation in high temperature environments