The assortment of species of tiny soil animals - small enough to stand on the head of a pin - differ from one urban park to another, unlike plants and larger animals where a few species are often found across many parks. This suggests that park managers should tailor management strategies to achieve better soil health, according to a published study of parks in Rochester, New York.
These soil creatures, including mites and springtails, collectively known as microarthropods, are a critical link in soil food webs. They eat microbes and are prey for larger organisms. They also cycle nutrients and carbon within the ecosystem, especially carbon, as they disperse nutrients back in the soil when they die. Their abundance and diversity can serve as a bellwether of the overall health of a soil ecosystem.
The paper, "Soil Animal Communities Demonstrate Simplification Without Homogenization Along an Urban Gradient," published Oct. 16 in the journal Ecological Applications.
The presence of concrete, buildings and people often reduce the biodiversity of larger animals and plants; the same few species are likely found across many places along the urban landscape. The authors expected similar results for microarthropods in urban parks, but instead found that species diversity and community composition differed from one park to another.
"We expected that the urban parks that we sampled would have very similar communities and that more rural parks with less urbanization pressure would have more unique communities, but that's not what we saw," said Hayden Bock, Ph.D. '24, the paper's first author and a former doctoral student in the lab of Kyle Wickings, associate professor of entomology in the College of Agriculture and Life Sciences and the paper's senior author.
"We actually saw that in the highly urban city centers, the microarthropod communities are more unique and have less overlap between them," said Bock, now a postdoctoral researcher at Pennsylvania State University.
"Our study demonstrates that although urbanization can have negative impacts on soil biodiversity, city parks can still support rich and unique belowground microarthropod communities," Wickings said. "This is especially important in cities where greenspace is often limited."
The result challenges the established idea that urbanization creates predictable homogenized ecological communities, and points researchers toward reconsidering this theory in more nuanced ways, Bock said. The authors attributed the break in the pattern found with other organisms in urban parks to the diminutive size of microarthropods.
"They are so small compared to the scale of the city," he said. "It's seven orders of magnitude difference, as we measure cities in kilometers or miles and we measure microarthropods in fractions of a millimeter."
As a result, they can exist in highly intact communities, even within the most disturbed urban landscapes, he said.
In the study, the researchers investigated the influence of urbanization on soil animal communities in 40 public parks along a gradient from rural to urban in the Rochester area. They collected samples in spring and fall over a two-year period, and evaluated microarthropod abundance, diversity and community profiles, and related this data to urban and soil characteristics at each park.
They collected more than 120,000 individual specimens across all parks; Bock spent the better part of two winters identifying specimens under a microscope.
"Not many people look at these animals, because they are incredibly difficult to accurately identify," Bock said. "Beyond that, it takes a very long time because they are so small."
Bock also analyzed these microarthropods' isotopic signatures, which revealed specific ecological functions they were performing.
"Understanding that even highly urban parks are still incredibly diverse necessitates that we implement strategies that can preserve biodiversity, because those green spaces provide many beneficial ecosystem services to people who live near those areas," Bock said.
Co-authors include Peter Groffman at the Cary Institute of Ecosystem Studies, and Jed Sparks and Frank Rossi, both at Cornell.
The study was partly funded by the New York State Turfgrass Association and the Cornell Atkinson Center for Sustainability.
