Groundwater influence on vegetation: water source, waterlogging, or both?

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From a broad, global-to-hillslope perspective, I will discuss some observational evidence and model results suggesting that the groundwater can directly influence vegetation through three mechanisms: as a water source for plant root uptake in dry places/times where/when the water table is accessible, as a cause for waterlogging and soil anoxia where/when the water table is too near the surface, and as a double-stressor if the water table fluctuates wildly, too deep in dry times but too shallow in wet times. as a water source for plant root uptake in dry places/times where/when the water table is accessible, as a cause for waterlogging and soil anoxia where/when the water table is too near the surface, and as a double-stressor if the water table fluctuates wildly, too deep in dry times but too shallow in wet times. The dominance of each mechanism, and the resulting mode of vegetation feedback, can be analyzed in a 2D space, with the climate on one axis, and the topographic structure on the other, forming a climotopo-matrix to frame the distinct modes of groundwater-vegetation interactions. On top of this framework, the subsurface structure of the Critical Zone forms a 3rd dimension that regulates the infiltration and water table depths, further enriching the models of groundwater-vegetation interactions. I will end by posing a set of hypotheses as food for further thoughts.