Global change includes both climatic change as well as changes in land use and in biodiversity. The impact of climatic environmental stresses and land use pressure on grasslands are not well known. Grasslands are expected to undergo the largest changes in diversity, as they are affected simultaneously by a combination of factors [e.g. nitrogen (N) deposition, overgrazing, increasing of atmospheric CO2 concentrations and temperature]. This is particularly significant since grasslands constitute a major pool of the global C cycle, accounting for 20% of the terrestrial CO2 fluxes and contributing to a similar share of the global soil organic C. Until today rather few studies have considered the combined effects of increased temperature and 1) drought stress, or 2) increased N deposition rates on loss of diversity.
The proposed project aims to investigate the outcome of these combined effects on diversity loss and on C and N cycles, including C and N plant-soil allocation, during different stages of plant development. Specifically, we will evaluate (1) the performance, productivity, and water use efficiency, (2) soil C balance, and (3) different aspects of the N cycle and plant N-use efficiency, all in different types of grassland communities. Several experiments will be performed using model ecosystems grown in 12 sunlit, climate-controlled chambers. Each chamber will contain 24 plant communities, with different combinations of nine grassland species: three grass species, three N-fixer dicots and three non-N-fixing dicots.
Each plant community will consist of one, three, or nine species, in order to simulate different species richness levels. Half of the chambers will be exposed to ambient air temperatures, while the other half will be warmed by 3ºC. The proposed study will advance our knowledge of how ecosystem diversity will respond to stresses in a future climate, and will contribute to reducing the current uncertainties surrounding diversity loss in grasslands.
Fields of science
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