Autumn and spring fires on the prairie contribute to the reproduction of Echinacea angustifolia, as they synchronize the flowering of different specimens, scientists write in the Proceedings of the National Academy of Sciences. This is one of the first studies to look at the direct effects of fires on a particular plant species.
Steppes, prairies, pampas, savannas are herbaceous communities with an arid climate, in which unexpected patterns often operate. For example, the long absence of fires is known to reduce the species diversity of plants on the prairie. However, why this happens, what are the mechanisms of maintaining the abundance and diversity of grasses due to fires, is very poorly studied.
Employees of the Botanical Gardens of Chicago and the University of Wisconsin in Madison monitored 778 periodically flowering specimens of Echinacea angustifolia for 21 years in a row, from 1996 to 2016 inclusive. It is a perennial plant with well-visible basket inflorescences that are pollinated by various types of bees and other insects.
Observations were carried out at two sites (distance between their boundaries 40 meters) in a protected area of tall grass prairie in Douglas County, Minnesota. For a long time they tried to prevent fires there. But during the observation period, the rangers arranged controlled fires of this or that area about once every five years.
Scientists annually noted when each particular specimen of echinacea began and finished to bloom, how these dates differed from those that were noted for neighboring plants of the same species as on each specimen of baskets. They also counted the number of seeds that each plant produced per year.
It turned out that in years with spring fires and years after autumn fires, Echinacea blooms more synchronously (P <0.001) than in years without them. Therefore, it has more blooming neighbors (P = 0.002) and is more likely to be pollinated. Moreover, each plant produces more baskets and seeds (P <0.001) if there is a fire before flowering. Within one year, the proportion of flowering individuals is higher where it fell.
Researchers do not know what the physiological mechanisms of echinacea bloom synchronization are in years with fires. The number of pollinators did not seem to depend on whether it passed or not, and rodents eating the seeds of this plant were noticed only once in all years and only at one point of observation. It is also interesting that some other types of echinacea are affected by fires, their number declining in the years with fires.
The authors themselves advocate expanding research on the effects of fires on the species diversity and abundance of specific plants in isolated areas of prairies where fires have been holding back for a long time. It is likely that on some of them, fire can increase the number of individuals of certain species - and this will be useful, since most of the prairies are now in decline.
In Russia, unplanned forest fires have a great influence on the state of natural communities, if only because most of the country's territory is occupied by forests. However, here, in contrast to the case with echinacea angustifolia, the consequences are rather negative. Read about the scale of forest fires in our country and how dangerous they are in our material "Theme - Fire".