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Background and aims: Plant productivity in drylands is frequently co-limited by water and nutrient availability, and thus is expected to be influenced by ongoing changes in rainfall regime and atmospheric nutrient deposition. Roadside grasslands are widespread worldwide, represent ecologically meaningful examples of highly dynamic anthropogenic ecosystems, and are well suited to investigate global change effects on plant performance. We evaluated the effects of changes in water and nutrient availability on the relative dominance and physiological performance of Bromus rubens, Carduus tenuifolius and Melilotus officinalis, which belong to contrasting functional groups (grasses, non-legume forbs and legumes, respectively). Methods: We conducted a factorial field experiment in two semiarid roadside grasslands in central Spain with the following factors: watering (no water addition vs. watering with 50% of the monthly total precipitation median) and fertilization (no fertilization vs. addition of 80 kg N ha year). The cover of the species evaluated, was surveyed over a 2-year period. Plant isotopic composition (leaf δC and δO) and nutrient concentrations (foliar N, P and K) were used to assess plant ecophysiological performance. Results: Carduus was able to cope with lower water availability levels through stomatal adjustments without a significant reduction in its relative dominance. The relative dominance of Bromus was negatively affected by even moderate water stress, although elevated nutrient deposition buffered the adverse impact of drought through a nutrient-mediated enhancement of plant water use efficiency. Increased nutrient availability strongly decreased the relative dominance of Melilotus, irrespective of water availability. Conclusions: Species-specific physiological mechanisms of adjustment to treatments suggest that plant communities in roadside grasslands will not respond as a unit to global environmental change. The characterization of species-specific responses to major global change drivers may improve predictions about the future dynamics of plant communities in novel ecosystems such as roadside slopes. [ABSTRACT FROM AUTHOR]

Identifying forage species that are productive in saline environments is an important research priority in many areas of the world affected by salinity. The salt and waterlogging tolerances of 19 species of Melilotus were evaluated in a series of glasshouse experiments. Measurements taken on each species included: dry matter (DM) production, root growth and development, shoot ion (Na+, K+ and Cl−) concentrations, root porosity, and in vitro estimates of nutritive value. Research on several species was restricted because of their potential as weed risks. Of the remaining species, M. siculus (syn. M. messanensis), an annual species, showed high relative salt and waterlogging tolerances, good DM production under non-stressed and stressed (saline and hypoxic) conditions, a high level of root porosity under stagnant conditions, low tissue ion (Na+, Cl−) concentrations, and a reasonable dry matter digestibility content (range 66–69%) under highly saline conditions. M. sulcatus ssp. segetalis and M. indicus were also identified as species with good DM production and tolerance to salinity and waterlogging stresses. Further weed risk assessments and field trials on these species are required before they can be promoted for use as pasture forages on saline areas. [ABSTRACT FROM AUTHOR]

Studies nitrogen mineralization and crop uptake of 15N labelled red clover and yellow sweetclover plant fractions. Measurement of 15N recovery in spring wheat and lolium perenne; Condition when maximum nitrogen mineralization was observed; Contribution of different plant parts and age in nitrogen mineralization.