Wildfires Stimulate Flower Power in Prairie Plants

Wildfires are often destructive, but some plants have adapted to benefit from the flames. A recent study by Lea Richardson and colleagues, published in the American Journal of Botany, found that fires significantly increased flower and seed production in two types of prairie plants, Narrow-leaved Purple Coneflower (Echinacea angustifolia) and Rough Blazing Star (Liatris aspera). However, a related flower, the Showy Goldenrod (Solidago speciosa), showed no improvement from fires.

The research provides new insights into how wildfires influence plant reproduction. Fires can clear debris, release nutrients, and synchronise the flowering of different plants. All of these effects can improve pollination by increasing the availability of resources for plants and the opportunities for cross-pollination between them. However, not all plants respond the same way to fires, which can impact the overall plant community.

To explore how fire influences prairie plants, researchers monitored purple coneflower, blazing star, and goldenrod at a preserve over multiple years, some with controlled burns and some without. They counted the number of flowering stems, flowers, fruits, and seeds for each plant after fires and tracked how well the different species produced seeds, a measure of reproductive fitness.

Plants that experienced fires produced more flowers and seeds in the purple coneflower and blazing star but not the goldenrod. A question was whether it was improved resources or improved pollination opportunities that increased reproductive fitness. Richardson and colleagues say it is probably both.

The botanists point to the increased number of flower heads and fruits as evidence of a resource boost for the coneflowers and blazing stars. However, Richardson and colleagues caution against identifying the actual fire as the source of this resource boost with total certainty. They write:

Despite the relationship we detected whereby head counts in E. angustifolia and L. aspera increased with fire, we can’t be sure that a post-fire boost in resources is responsible. A non-resource trigger may induce plants to invest more stored resources in flowering than they would in a year without the fire cue. For example, aspects of fire that may cue flowering could include exposure to smoke or heat.

Richardson et al. 2023

Another way the plants benefitted was through improved pollination. All the extra flower heads meant plants had more potential mates to send their pollen to. The fire also effectively synchronised the plants to flower around the same time, improving the chances for cross-fertilisation.

In contrast, fires did not affect the goldenrod, implying that the species has not adapted to take advantage of the post-fire environment. The results suggest that while many plants flower more after fires, the reproduction benefits depend on both the availability of resources and synchronised flowering with other plants nearby. The inconsistent responses between closely related species could significantly impact the local ecosystem.

The findings reveal the complex effects of wildfires on plants and the surrounding community. Although fires are disruptive, for some species, they can be vital in stimulating flower power and seed production. A better understanding of how different plants respond to fires could inform conservation and ecosystem management.

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Richardson, L.K., Beck, J., Eck, D.J., Shaw, R. and Wagenius, S. (2023) “Fire effects on plant reproductive fitness vary among individuals reflecting pollination-dependent mechanisms,” American Journal of Botany. Available at: https://doi.org/10.1002/ajb2.16160.