Slogging home from work, you may be annoyed when you track mud into the house. But, before you wipe the grime away, have you ever considered the world clinging to the heel of your shoe? Scientists have long contended that soil is the most diverse and species-rich environment on the planet. Until recently, this ecosystem has remained poorly described. So why would anyone want to study mud?
Soils are incredibly important. Soil provides a medium for growing plants, regulates water supplies, recycles nutrients, and provides a home for a plethora of organisms. Understanding the diversity that exists in the realm below our feet can help scientists understand the ecology of this undiscovered country.
A recent study examined soil samples from Central Park in New York City. Central Park consists of more than one square mile of highly managed urban ecosystem. It has more than 350 plant species, 250 vertebrate species, and 100 invertebrate species above ground. With an ecosystem that has been manipulated by humans for over a century, one might expect that the biodiversity below ground to be rather homogenous. On the contrary, scientists determined that the soil in the most visited park in the largest city in the United States is incredibly diverse. The samples contained more than 122,000 bacterial, 1,500 archaeal, and 43,000 eukaryotic microorganisms. Many of the organisms identified in the soil samples were unknown in the scientific literature.
But how does the park soil compare to the rest of the world? The scientific team compared the park soils to a global soil set consisting of 52 diverse soils from around the globe. The Central Park soil samples presented a community of microorganisms as diverse as soils from the tropics to the temperate forests to the grasslands to the tundra.
What is fascinating is the lack of continuity between adjacent soil communities within the park. This geographic discontinuity may be a result from the management practices used in the park. The highly manipulated structure of the park promotes microorganism diversity within the soil. The biggest difference between the park soils and the global soil set is the presence of human pathogens, such as Salmonella enterica and Staphylococcus, in the park soils. The pathogens in the soil cannot cause disease and are most likely a result of the pressures from the large urban system surrounding the park.
Long story short—if you are looking for an unknown world to discover, look no farther than your back yard and say hello to your little friends.
Featured Image: Research team member takes a soil sample in Central Park. Credit: Noah Fierer