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D'Acunha, Brenda Melissa

University of British Columbia

Tropical ecosystems are key in regulating global carbon (C), water and energy budgets, and are thus central to the global climate system. However, deforestation and land-use and land-cover change (LULCC) continue to rapidly expand in these areas, negatively affecting the ecosystem services they provide. Understanding how C and water fluxes and their main drivers and controlling mechanisms vary depending on biome and land-use change is crucial to predict the effect that further changes in land use and climatic conditions could have on these ecosystems (and by extension, the global climate system). Moreover, this information can be used to develop policies for climate change mitigation and land management. However, our understanding of tropical ecosystems is still limited, mainly because fluxes and their controls can vary greatly due to multiple, interacting factors, and the lack of ground observations. This thesis investigates the effects of LULCC on C and water fluxes using a network of eddy covariance towers located across the state of Mato Grosso, Brazil, including flux towers in natural and managed sites within Amazon forest, Cerrado savanna and Pantanal wetland biomes. Data from the tower network showed that water limitations caused a reduction in carbon and water fluxes during the dry season, particularly in managed sites. Fluxes at natural sites had a strong correlation to a mix of biotic (leaf area index) and environmental drivers (radiation, temperature, soil water content), whereas fluxes were tightly correlated to crop cycles at managed sites. LULCC changed the seasonality of both carbon and water fluxes, which could eventually increase precipitation variability in the region. Increasing the intensity of management (i.e., using irrigation and incorporating cover crops into crop rotations) increased carbon uptake and evapotranspiration, but climate conditions, the choice of cover crop and the time of planting all affected the magnitude of C and water fluxes. The information in this thesis can be used to parameterize and validate climatic models and remote sensing products to improve current and future predictions of carbon and water fluxes, and also to inform management policies in the region.

Text

2022-08-12

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82358

Geological Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/