would be 2,166 tonnes (an increase of 0.7%). Of added concern are the longer-term consequences of continual deterioration of pasture quality and the implications for changes in farming practices to compensate for potential reductions in livestock production capacity.

Northern hemispheric background concentrations of ozone are increasing, but few studies have assessed the ecological significance of these changes for grasslands of high conservation value under field conditions. We carried out a 3-year field experiment in which ozone was released at a controlled rate over three experimental transects to produce concentration gradients over the field site, an upland mesotrophic grassland located in the UK. We measured individual species biomass in an annual hay cut in plots receiving ambient ozone, and ambient ozone elevated by mean concentrations of approximately 4 ppb and 10 ppb in the growing seasons of 2008 and 2009. There was a significant negative effect of ozone exposure on herb biomass, but not total grass or legume biomass, in 2008 and 2009. Within the herb fraction, ozone exposure significantly decreased the biomass of Ranunculus species and that of the hemi-parasitic species Rhinanthus minor. Multivariate analysis of species composition, taking into account spatial variation in soil conditions and ozone exposure, showed no significant ozone effect on the grass component. In contrast, by 2009, ozone had become the dominant factor influencing species composition within the combined herb and legume component. Our results suggest that elevated ozone concentrations may be a significant barrier to achieving increased species diversity in managed grasslands.

Seed losses from imported oilseed rape (OSR) and the genetically modified (GM) admixtures therein may potentially lead to the establishment of transgenic plants and their hybridization with wild crucifers. The post-market environmental monitoring (PMEM) must therefore also address problems related to seed spillages of GM OSR. Since detailed information on imported commodity flows, GM contents, means of transport, downstream users and efficient containment of GM OSR was lacking, we performed a field study in the vicinity of large oil mills and seed processing industries at the harbours along the river Rhine. One hundred thirty-six composite samples taken from one to 20 plants per site were collected near roads, railways and waterways. Individuals or large groups of feral OSR plants were detected in all of the nine study areas, but only one plant out of 1918 tested was confirmed to be transgenic (GT73). The results suggest that a spread of herbicide tolerant GM OSR has not occurred to date. In order to confirm the absence of GM feral OSR and potentially adverse effects of GM plants in the future, we recommend monitoring feral OSR on a routine basis. We present an approach for the sampling and testing of feral OSR that is based on floristic mapping and rapid tests for the determination of herbicide tolerances.

Background and Aims Differential capacity of species/ genotypes to respond to increased atmospheric N deposition may be an important long-term driver of species composition change. In this study, differences in response to atmospheric N deposition were analysed for different accessions of Prunella vulgaris. Methods P. vulgaris plants deriving from different N deposition accessions (0-15, 15-25 and 25-35 kg N ha −1 yr −1 ) were exposed to different N treatments (10 or 30 kg N ha −1 yr −1 ), with and without competition with the grass Bromus erectus. After 8 months, plant performance and differences in competitive ability were determined. Results Strong effects of accession were found, often in interaction with N treatment: P. vulgaris plants from populations with low N deposition backgrounds often outperformed plants from medium to high N backgrounds, illustrated by greater biomass at high N treatment and higher chlorophyll and leaf N concentrations at low N treatments. When grown in competition, however, a strong decrease in biomass was observed for plants from all accessions. Conclusion All accessions of P. vulgaris showed a low competitive ability. Plants from low N accessions proved to be most sensitive to competition in terms of root biomass. However, in the absence of competition, low N accessions showed a greater plasticity in nitrogen use efficiency. These results illustrate the importance of including accession when considering effects of N deposition.

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