Water, Climate, and Vegetation: Ecohydrology of a Changing World

Wednesday, November 3, 2010 - 4:30pm
Drew Guswa, Director and Associate Professor
Director - Center for the Environment, Ecological Design and SustainabilityAssociate Professor - Picker Engineering Program


One challenge of the emergent field of ecohydrology is the bringing together of the continuum approach of hydrology with the object-oriented perspective of ecology.  The science of complex adaptive systems is one framework that can provide some insight to this integration.  One feature common to complex adaptive systems is the tradeoff between tracking and averaging behavior, i.e., responding rapidly to environmental change or damping out environmental forcing.
Root uptake of soil moisture exhibits such a balance of tracking behavior (or intensive use) and averaging behavior (or conservative use) that depends on species.  A focus on resource exploitation – a maximization of net carbon benefit – allows one to predict an optimal root depth as a function of this behavior, along with the nature of the climate, soil texture, and other plant characteristics.  Relative to conservative water-use, intensive use leads to shallower roots and higher rates of carbon assimilation at the expense of drier soil conditions.  For both water-uptake strategies, the deepest roots arise when precipitation and potential evapotranspiration are approximately equal.
Contrary to plant roots, which generally act to homogenize soil moisture, vegetation canopies intercept and redistribute precipitation in space.  While patterns are challenging to correlate with canopy characteristics, examples from hemlock and deciduous forests in the northeast United States indicate that spatial patterns vary with species and are temporally persistent.  This persistence produces wet and dry regions in the soil that may affect non-linear processes of recharge and biogeochemical transformation.