Plant-mediated hydraulic redistribution: a valve controlling watershed solute transport?

Roots can move water from wetter areas to drier areas in soil. This process is called hydraulic redistribution and has been observed around the world. This movement of water can change how soil holds carbon and how soil particles are arranged. The size and arrangement of soil particles controls how water moves through the ground and to streams. As water moves through the ground it transports nutrients and it can also transport pollutants. Small changes to the arrangement of soil particles can have large impacts on the amount of water in streams and the nutrients and pollutants carried to the stream. This three-year award will focus on testing three hypotheses at the well-studied H.J. Andrews (HJA) Experimental Forest. First, the structure of soil will break down where hydraulic distribution creates wetter conditions. This breakdown is a result of an increase in the decomposition of organic matter and a decrease in soil water salt concentrations. Second, a greater portion of soil organic carbon will be lost in water as dissolved organic carbon as compared to gas as carbon dioxide

carbon dioxide (CO2)

An important heat-trapping gas, also known as a greenhouse gas, that comes from the extraction and burning of fossil fuels (such as coal, oil, and natural gas), from wildfires, and natural processes like volcanic eruptions.

Source: NASA Source

where hydraulic redistribution creates wetter soils. Finally, wetter conditions created by hydraulic redistribution will increase the loss of nutrients and weathering products transported to the stream. 

To test our hypotheses, we will use greenhouse experiments and field observations to measure changes in soil structure, properties, and chemistry. We will rely on mathematical models to better understand how variable water, nutrient, and metal fluxes

flux

The amount of some type of particle or energy crossing a unit area per unit time.

Source: NRC Library Source

are to changes in hydraulic redistribution. Our efforts will involve the development of new geophysical methods to measure water fluxes related to hydraulic redistribution in greenhouse and field settings.  Together, these data and models will be used to quantify how variations in hydraulic redistribution influence fluxes of carbon, nutrients, and metals from the critical zone to the stream. This effort will involve the collaboration of ecohydrologists, ecosystem

ecosystem

A natural community of plants, animals, and other living organisms and the physical environment in which they live and interact.

Source: A student's guide to Global Climate Change Source

ecologists, geophysicists, geochemists, and environmental engineers from Oregon State University, Colorado School of Mines, University of Colorado Boulder, Pacific Northwest National Lab, and Pennsylvania State University. Results from our study will improve mathematical models of water movement and chemistry, and increase our understanding of the water cycle and water chemistry.