Simoes Barneze, Arlete (2018) Interactive effects of climate change and management on grassland greenhouse gas emissions. PhD thesis, UNSPECIFIED.
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Abstract
Climate warming has the potential to alter carbon (C) and nitrogen (N) cycling affecting greenhouse gas (GHG) emissions and a range of other ecosystem functioning in grasslands. This will be particularly important for the sustainability of agricultural ecosystems due to its role in global food security and soil C sequestration. The interaction between climate warming and grassland management is highly important and needs to be addressed as it may change the direction and strength of the effects on GHG emissions by changing plant productivity (either above and/or below-ground) and plant-soil properties. Plant species composition also plays a key role affecting the nutrient cycling thus GHG emissions in grasslands. The aim of this thesis is to understand how grassland management will influence C and N cycling under future climate change. The interactive effect of climate warming and grassland management is investigated in a field experiment over two growing seasons with varied microclimate effects, and the effect of plant composition manipulation in a controlled temperature mesocosm experiment. Overall, interactions between warming and management significantly affected GHG fluxes and plant-soil properties with important single treatment effects. The role that below-ground components plays on GHG emissions was less evident, becoming unclear the mechanisms related to gas releases to the atmosphere. Increases in legume proportions in grass-legume mixtures reduced ecosystem respiration in fertilised soils, with no effects in unfertilised soils. N cycling was not affected by increases in legume proportions. Plant productivity including above- and below-ground biomass had a non-linear relationship with relative legume proportion. Either grassland management or different plant species compositions approach may improve C sequestration and reduce GHG emissions.