Vegetation drives greenhouse gas exchange, and carbon and nitrogen cycling in grassland ecosystems

Abstract

Grasslands are the most widespread habitat in the world, and play a crucial role in climate change mitigation. However, predictions about greenhouse gas (GHG) fluxes, and carbon (C) and nitrogen (N) cycling, are still marked by great uncertainty, which in good part lies on soil – vegetation interactions. Accrdingly, this thesis investigates the role of vegetation, in terms of phenology, structure and diversity, as a driver of GHG exchange, C and N cycling in grasslands along a climatic gradient (mountain grasslands and dehesa ecosystems) and under diffrent management regimes. GHG recording was done combining continuous (eddy covariance) and discrete chamber based measurements. C and N cycling was assessed using C and N content, and 13C and 15N isotope ratios as a proxy. Our results showed that vegetation influenced GHG fluxes and C and N cycling along the climatic gradient and management regimes. In mountain environments, phenology determined interactions between CO2 exchange, vegetation and environmental variables, depending on the elevation belt. In dehesa ecosystems, the tree – open grassland structure drove CO2 and N2O fluxes, with some differences among tree species. Moreover, the different plant functional types, presented marked differences in their C and N acquisition and use strategies. Legumes enhanced net CO2 uptake and N2O emissions; as well as cereal – legume interactions enhanced net CO2 uptake compared to cereal monocultures. Overall, the inclusion of vegetation structure and diversity improved the understanding of mechanisms affecting GHG exchange, and C and N cycling.

Date of Award	9 Jan 2020
Original language	English
Awarding Institution	University of Lleida (UdL)
Supervisor	Mª Teresa Sebastiá Álvarez (Director) & Angela Ribas Artola (Director)