Temperate grasslands and global atmospheric change:: a review

Recent reviews confirm and extend previous observations that elevated carbon dioxide (COD concentrations Stimulate photosyn thesis, leading to increased plant productivity. Elevated CO2 concentrations tend to reduce the sensitivity of grassland ecosystems to low levels of precipitation but induce progressive nitrogen (N) limitations on plant growth which can be alleviated by supplying a significant external input of N in the form of mineral fertilizer or through the increased use of N-fixing legumes. Other nutrients, such as phosphorus, can act as the main limiting factor restricting the growth response in legumes to atmospheric CO2 concentration. The botanical composition of temperate grasslands is affected by the rise in atmospheric CO2 concentration, possibly through a decline in the relaTive abundance of grasses. Elevated CO2 concentration will also alter the feeding value of herbage to grazers both in terms of fine-scale (for example, crude protein concentration and C:N ratio) and coarse-scale (legumes vs. grasses and C-3- VS. C-4-species) changes. The management guidelines of grasslands will need to be adapted to global atmospheric and climatic changes and to increased variability in climate.