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Despite their ecological, economic and social importance, grasslands in areas with Mediterranean climates continue to receive limited scientific, political and media attention. The main objectives of this review are to compare and contrast dryland grasslands in the 'Old World' regions of the Mediterranean basin (southern Europe, western Asia and North Africa) with those of 'New World' regions with Mediterranean climates (Australia and Chile) and to identify common research priorities. The common characteristics and differences in climate, soils, native vegetation, importance of the livestock sector and the socio-economic background for the different Mediterranean environments are examined. Past trends and the current status of temporary and permanent Mediterranean grasslands are also described. Some common issues between these regions are as follows: (i) adaptation to climate change; (ii) increasing persistence and drought survival of both annual and perennial species; (iii) the important role of forage legumes; (iv) maintaining grassland plant diversity; and (v) improved ecosystem services, such as carbon sequestration, control of soil erosion and wildfires, and preservation of both wild and domestic biodiversity. The favourable climate in these regions, which allows year-round grazing and the growth of legumes, should be exploited to improve the sustainability of grassland-based, extensive farming systems and the quality of their animal products, while at the same time improving ecosystem services. The decreasing support for grassland research and development programmes requires increased international scientific and technical cooperation among the few institutions operating in the different Mediterranean-climate areas of the World to provide innovative and sustainable solutions to farmers. [ABSTRACT FROM AUTHOR]

A study was conducted on the effect of tropospheric ozone ( O3) on soft brome ( Bromus hordeaceus) and the modulation of its response by nitrogen ( N). Two assays were conducted using open-top chambers ( OTCs). Three O3 treatments were considered: filtered air, with concentrations below background levels (charcoal-filtered air), non-filtered air ( NFA) that simulates ambient O3 concentrations, and unfiltered air to which 40 nL L−1 O3 above-ambient concentrations was added ( NFA+), simulating elevated values recorded in natural areas of annual pastures in the Iberian Peninsula. Three N rates were used, simulating the increase in soil N through atmospheric deposition and excreta from livestock grazing. Ozone caused an augmentation in foliar senescence, whereas green biomass was not altered; consequently, an increased senescent/green biomass ratio was produced. A stronger O3 effect was detected in the second assay compared with the first. This was related to the estimated absorbed O3 fluxes, which were double the value calculated in the former. Increasing N input enhanced biomass production, but its effectiveness was greater in the first assay, under less-favourable weather conditions and lower plant growth. In the first assay, the O3 response was modulated by N availability, which mitigated the effects of O3 to medium concentration values. In the first assay, O3 reduced the aerial/subterranean biomass ratio, caused by a positive-trend effect on roots. Foliar concentration of lignin was increased by O3, and in vitro digestibility of aerial biomass and the plant cell wall fraction tended to decrease with increasing O3. [ABSTRACT FROM AUTHOR]

There is limited information on the effects of the increase in the density of shrubs on herbage production and nutritive value of natural grasslands in the Mediterranean region, currently facing major land use changes. Herbage production of drymatter (herbaceous fractions, of plant functional groups and by species), crude protein (CP), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), acid-detergent lignin (ADL) and hemicellulose concentrations and in vitro organic matter digestibility were determined at the time of peak of annual growth across four types of grassland vegetation each characterized by different shrub cover regimes. A sharp reduction in herbage production and a reduction in nutritive value were found as a result of the increase in shrub cover. These changes appeared to be closely related to the shift in plant functional groups detected as shrub density increased. Herbage production from grasses and legumes was found to be more sensitive to shrub cover changes than herbage production from forbs, whereas, as grassland types became denser, annual species were gradually replaced by perennials and C4 grasses by C3 ones. The impact of shrub encroachment on Mediterranean grasslands is discussed in relation to their use by livestock. [ABSTRACT FROM AUTHOR]