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Home>Weed Research>IFAFS Project>Soil Features

Soil Isn't Just Dirt Handful of soil with a theoretical microscopic view of soil organisms

Soil can also be teeming with microscopic life. A thin layer of bacteria, mosses, and lichens at the soil surface is called microphytic crust. This affects several environmental processes including nitrogen fixation, soil erosion, water infiltration, seed germination, and plant growth. Other microbes within the soil help decompose organic matter, affect nutrient cycling, and form beneficial associations with plant species.



Two photos showing soil pits dug in native and cheatgrass dominated sites

There are many different types of soil, classified into 'species' just like plants and animals. Some soil is sandy, other types are made of fine clay particles. There are soils with lots of organic matter, and others with very little. Soil pH and chemistry can vary greatly, and have profound effects plants.

What happens to soil when weeds invade?
When weeds invade, they directly and indirectly alter the soil environment. IFAFS scientists are studying how soil changes as a result of cheatgrass invasion. They have taken soil samples, and dug soil pits in both native and cheatgrass dominated areas. Properties of the soils are compared and analyzed.


A unique tool called a resin capsule helps to evaluate soil chemistry and monitor how chemistry is altered by study treatments. For example, applying sugar Picture of a resin capsule next to a pennyto a study plot may reduce the amount of available nitrogen. Resin capsules are buried in treated (sugar added) and untreated (sugar free) soil. The capsules absorb the available nitrogen around them in the soil. The capsules from treated and untreated areas can then be compared for nitrogen content to see if the sugar addition really did reduce the amount of nitrogen available in the soil.


What about soil microbes?
Picture of microbiotic crust If weed invasion can alter soil properties, what happens to soil microbes? This question is also being looked at in the IFAFS study. Scientists are evaluating population levels of various types of microbes to highlight differences between weed-dominated and native plant communities. In addition, they are looking at the impact that study treatments and restoration measures have on both microphytic crusts and soil microbes.

Images:
-Soil microbes:Public domain.
-Soil pits:IFAFS photo .
-Resin capsule:IFAFS photo.
-Microphytic crust:Nicole Decrappeo.
-Sidebar photo:Nicole DeCrappeo.

Photo of Nicole DeCrappeo
Nicole DeCrappeo

I grew up in Pennsylvania as a die-hard Penn State fan, but moved to Washington, D.C. to attend American University. My goal in those days was to become the first female president of the United States. I ended up with an environmental studies degree instead, so I moved to Florida to work as an AmeriCorp volunteer studying nematodes in fig trees. That experience blossomed into a love affair with soil and microscopic soil critters.

I received my M.S in Ecology from Colorado State University. I now work for the U.S. Geological Survey in Corvallis, OR. I am also a Ph.D. student in the Soil Science Department at Oregon State University.

My IFAFS research involves studying how the soil is affected by cheatgrass invasion. I am interested in how soil community composition changes with invasion, and whether there are biological thresholds from which the soil community can’t recover on a human timescale. I am also interested in what factors are important in structuring soil communities (i.e. particular plant species, root exudates, rooting morphology, nutrient status), and whether we can use the native soil organisms to enhance our restoration efforts.