Impacts of Climate Variation and Change on Hydrologic and Vegetation Dynamics

Human-induced changes in climate and landscape characteristics are driving the coupled climate-hydrological-ecological system (CHES) into unchartered territories, with major implications on natural resource availability and sustainability at both local and global scales. Given that soil-plant-atmosphere are part of a hydrologic continuum, the variability and changes in climate may impact hydrological states and fluxes, which in turn can increase vegetation stress potentially resulting in an abrupt regime shift in the ecohydrological system. Describing and predicting the non-linear dynamics of CHES is challenging in part due to uncertainties in the parameters that describe the system and insufficient understanding of the physical mechanisms that control these responses. This dissertation strives to bridge these gaps through synergistic use of data analytics and physically-based modeling so as to characterize a spectrum of dimensionality, nonlinearity, and stochasticity of CHES across a range of spatial-temporal scales. Three overarching questions frame the direction and scope of this dissertation: Q1 – how do meteorological conditions affect groundwater dynamics in forested wetlands? Q2 – how to evaluate forest mortality risk under long-term climate change, and predict near-term forest mortality? Q3 – how does plant hydraulics regulate plant water use under hydro-climatic stress across biomes? Addressing these questions will improve the understanding of CHES dynamics and representations of hydrologic and vegetation dynamics in Earth System Models. The findings and methodologies developed here can be leveraged for devising mitigation and adaptation strategies for water resource management and ecosystem conservation under current and future climate regimes.