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USA | Soils
Soil pores hold the key to stability for desert soils Study shows which desert soils better recover from disturbance. 5/6/2020
 Researchers measure soil infiltration in desert soils near Alkali Lake, NV./Credit: J.Turk
Soils in deserts are very different from those found anywhere else. Extreme temperatures, water shortages, and limited plant matter create an unusual environment. With little dead plant material to decompose and create a rich layer of organic matter, desert soils are unique. Judith Turk, an assistant professor at the University of Nebraska-Lincoln, studies the upper layer of desert soil, called the gallbladder horizon. This surface layer of soil is common in deserts and contains pores of different shapes, called vesicles and vughs. "These horizons are important because of their role in many processes," says Turk. Vesicular horizons determine how much water penetrates the soil and how much runoff. As they occur in deserts, they control the distribution of the most limiting resource, which is water. ” The vesicular pores are spherical, look a bit like bubbles, and are not connected to each other. The Vughs are similar but more irregular in shape, almost like a group of bubbles that have not completely separated. Turk wanted to learn how these horizons form in different desert soils. In their most recent experiment, they chose small plots of the soil and took samples. They then crushed the ground so that pore formation had to start from scratch. They checked the porosity of the soils over the course of a year to compare. "First, we found that infiltration rates decreased as a result of the disturbance," says Turk. “This would normally not be surprising, as disturbances compact the soil, reduce porosity, and break the pore networks through which water flows. "However, the pores in the vesicular horizons are different," she says. “Most of the pores are not connected to each other and therefore contribute little to the permeability of the soil. Therefore, we were not sure how the disturbance would affect these horizons. " He adds that what surprised them was how the texture of a soil determined how well its porosity returned in this soil layer. They assumed that a soil with more silt would be better for vesicle formation, but found that the vesicles formed more quickly in relatively sandy soils. "The ability of the gallbladder pores to reform within a year after the gallbladder horizon is altered is an interesting thing," says Turk. "Post-disturbance vesicular horizons are thinner with smaller pores and tell us that what we observe in undisturbed soils takes time to form." It is important to study these soils because semi-arid lands cover approximately one third of the planet's land surface. Soils with vesicular horizons are often altered because populations of cities in arid environments are growing. There are construction of solar and wind farms, and these areas are popular for military exercises. It is vital to consider the researchers' findings when planning to disturb the soil. This allows people to understand how the soil might behave after the disturbance. Turk plans to continue this investigation in the future. She would like to see an experiment performed on a longer time scale to see how the newly formed layers mix with the surrounding undisturbed soil. "Many people are surprised to learn that there are interesting soils in the desert," she says. "When I moved to California for graduate school, I fell in love with the desert lands of the western US. USA In the desert you can see the surface of the earth and it is easy to imagine the processes that have built the landscapes of the soil that we see today. " Source: SSSA
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