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I like to play with dirt!

October 29, 2013

Guest post by Viviana Penuela

When people ask me what I do for a living, is very difficult to answer without getting into a philosophical debate on what biology is. That’s because I study biogeochemistry – which might mean nothing to the average person – but is basically the study of how chemicals produced in biological processes cycle through the geological matrix of an ecosystem. At the end it’s just a fancy way of saying we like to play with dirt. But we call it soil and we don’t just like it, we LOVE it. Now admit it, when was the last time you considered what goes on inside the “black box” called soil?  The organisms in soil, from microbes to macro fauna, and the chemical processes they drive, are literally the foundation of many of the ecosystems we as scientists study. After all, few people realize that soil color is driven in part by decomposition of leaf litter by microbes.

So how does biogeochemistry fit into my research? For the biological component, I study fungi. These misunderstood individuals – mostly because they are understudied – play a big role as decomposers, soil engineers, symbiotes to plants, and parasites (yes, there’s also some bad guys). Fungi influence the chemistry of the soil by breaking down complex chemical into smaller components, transporting nutrients to and from plants and by physically influencing the composition of soil.

Fungi and soil interaction

Fungi and soil interaction

I am interested in understanding this last mechanism and how it influences the ability of soils to store carbon and other nutrients. Fungi serve as temporary support that lets soil particles come together and form clumps, also known as aggregates. In the process of aggregate formation, organic matter is embedded inside the clumps. By this mechanism, organic matter is locked inside the soil clump and is not easily accessible for microorganisms to eat or decompose. This way, the soil prevents nutrients from escaping out of the systems as by-products of insatiable microorganism or by filtering out of the soil. At the same time it increases the health by increasing the amount of carbon and nutrients stored in the soil.

Fungi serving as temporary support for soil aggregates

Fungi serving as temporary support for soil aggregates


Because fertility of soils is a big part of agriculture, most of the studies on soil aggregation have focused on agricultural land. Newer farming methods, such as minimal overturning of the soil, have come about in part by the need to not disrupt soils. Keeping soil clumps intact retains nutrients for future crops. But have you ever wondered what happens underground on your own backyard? I have, and this is the question that drives my research. I want to know if there are aggregates in urban soils, and how well they store organic matter. Do city fungi work as hard as the country fungi? Is the way you water your lawn affecting the formation of soil clumps? Could we have a better grass “crop” in our yards if we change our lawn care practices? These questions from urban ecosystems are yet to be explored and the best tools we have are ecological principles that we can apply to very familiar environments, in this case our own backyards.

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