A new study at Colorado State University revealed that one of the prominent herbivores of the Great Plains, black-tailed prairie dogs, may not cause long-lasting changes to vegetation and nutrient cycling on their colonies.
Colorado State ecology graduate student Laurel Hartley studied how colony die-offs due to bubonic plague mitigate the effects of black-tailed prairie dogs on plant communities and nutrient cycling.
"Prairie dogs are ecosystem engineers that alter their physical environment through grazing and burrowing. What we are learning now is that prairie dogs create a diversity of habitat on the prairie, but they do not necessarily permanently change the structure and function of shortgrass steppe," Hartley said.
Prairie dogs are highly susceptible to bubonic plague, which was introduced to the United States at the beginning of the 20th century and spread to western and central parts of the country by the 1940s.
"Before the plague, prairie dog colonies would live for decades. Now colonies are not nearly as old. Today colonies rarely go more than 10 or 15 years before they experience a plague outbreak. After an outbreak, colonies may not be re-colonized for five or more years," she said.
Through her research, Hartley found that plague causes a temporary release from grazing pressure by prairie dogs, and this release appears to mitigate the effects of a colony on shortgrass steppe structure and function.
"Shortgrass steppe does have some degree of resilience which is valuable in understanding management applications in terms of how people view prairie dogs on land," she said.
Hartley conducted her study by monitoring plant community composition, species richness, above-and belowground biomass, nitrogen mineralization and shoot, root and soil carbon. She collected her data from three recently colonized colonies, three recently abandoned colonies and three colonies older than 20 years.
A 25-year history of colony activity on the Pawnee National Grassland in Colorado shows that over half of all colonies will be subject to a plague event at least once every 20 years, affecting the diversity of habitat on prairies.
Prairies in the United States stretch from Canada down to Texas and range in grass types from short, mixed and tall. Shortgrass steppe is predominately in eastern Colorado and New Mexico and is typically dryer than tall and mixed grass, as well as being highly drought and grazing resistant.
Hartley presented her research at the Ecological Society of America annual meeting in Memphis, Tenn., earlier this month.
In the fall of 2006, Hartley will start her post-doctoral work at Michigan State University where she will coordinate a program for K-12 educators and continue conducting ecological research.