An Investigation of Interactions between Plants and Water, Energy and Carbon Budgets in the Soil-Plant-Atmosphere ContinuumLuo, Xiangyu (2014) An Investigation of Interactions between Plants and Water, Energy and Carbon Budgets in the Soil-Plant-Atmosphere Continuum. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractExchange of energy and substance (water, carbon dioxide, etc.) between land surface and atmosphere has a significant impact on climate. Considerable part of this exchange occurs through the soil-plant-atmosphere continuum (SPAC) where plants play an important role. Therefore functions of plants in water, energy and carbon cycles of the SPAC need to be extensively studied. When dry climatic conditions appear, plants can cope with the adverse circumstances by taking advantage of some biological or hydrological processes. In this study, the Three-Layer Variable Infiltration Capacity (VIC-3L) land surface model is extended to include some important biological or hydrological processes under water-limited climatic conditions: (1) movement of soil water from wet to dry regions through hydraulic redistribution (HR); (2) groundwater dynamics; (3) plant water storage; and (4) photosynthetic process. The extended VIC-3L model (referred to as VIC+ model) is evaluated with an analytical solution under simple conditions and with observed data at two AmeriFlux sites. Scenario simulations demonstrate that: (1) HR has significant impacts on water, energy and carbon budgets during the dry season; (2) Rise of groundwater table, increase of root depth, HR, and plant water storage can increase dry-season latent heat flux; (3) Plant water storage can weaken the intensity of upward HR; (4) Frozen soil can restrict downward HR in the wet winter and reduce the soil water reserves for the dry season. Groundwater can have significant impacts on the interactions between land surface and atmosphere by way of mechanisms such as influencing plant transpiration. The VIC+ model is used to conduct numerical experiments to study impacts of groundwater on transpiration. The relationship between transpiration and groundwater dynamics, and the related subsurface processes under various conditions are revealed and analyzed through results of numerical experiments. In order to predict interactions between land surface and atmosphere in the future, vegetation needs to be represented dynamically in modeling studies. To this end, the CASACNP biogeochemical model has been coupled with the VIC+ model. This coupled model is used to conduct scenario simulations to demonstrate impacts of vegetation on water and energy cycles when dynamic growth of vegetation is represented. Share
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