Fire Flora

Fire Flora

Anyone who has ever gardened or worked on their landscaping at home knows the mantra “right plant, right place”. We’d like to add “right time”. If you’ve ever tried to plant lettuce in the summertime, you know it’s an exercise in futility! Natural areas operate exactly the same way. There’s a reason that you won’t find a cypress tree in upland scrub habitat or a longleaf pine on the beach. Root structures, soil acidity, and water flow are all factors that contribute to an individual plant’s survival and a population’s ability to thrive in any given ecosystem. One fascinating factor that promotes healthy populations of some flora refers to plants that thrive with the presence of fire, or pyrophytes. There are several subcategories of this term:

Passive pyrophytes: resist fire with structures such as thick bark or deep root systems, making them extremely adaptable to areas that see frequent fire from lighting strikes.

Active pyrophytes: are dependent on fire to eliminate competitors who may encroach upon their habitat and compete for resources.

Pyrophiles: require the presence of fire to spread seed and reproduce.

And a bonus term:

Serotiny: refers to the ecological adaptation that encourages seed dispersion in response to environmental triggers, most notably fire.

pine bud

Previously we’ve gone over the numerous ecological benefits that prescribed fire brings to our nature preserves here in Hillsborough County. It is one of the most cost-effective land management tools we have to both suppress the effects of lightning-induced wildfire and keep fire-dependent ecosystems thriving. Since Florida doesn’t experience snowfall, invasive plant species can quickly overtake an area without intervention. Cogongrass, for example, is one of the most prolific invasive plants we deal with here in the county (although it is widespread all over the state). Treating units with widespread infestations with prescribed fire have shown remarkable effects; left to its own devices, cogongrass can completely eradicate any natural plant communities that were once present, severely threatening the ecosystem’s health. 

But why would anything want to live in an area that experiences frequent fire?

pine lily

As the lighting capital of North America, Florida’s ecosystems have experienced fire for thousands of years. The Florida Natural Areas Inventory notes that about 70% of Florida’s terrestrial natural plant communities are fire-dependent.  Fire contributes to soil acidity, reduces competition, promotes nutrients in the soil, and encourages seed dispersion (remember our term, serotiny). Some rare plants even grow only after fire events, for example, calopogon. These orchids (pictured right) can emerge in as little as two weeks after a fire event. 

calopogon

A once-common species, the longleaf pine, has extremely thick bark which protects it from extreme heat. Logging greatly reduced the numbers of longleaf pines in the Southeast; fire suppression has significantly reduced viable habitat. The pine lily (Lilium catesbaei) is endemic to the Southeastern Coastal Plain and is the largest North American lily. Fire benefits this species when it clears other plants from the area, creating wide-open sunny areas for it to grow. In some cases of wildfire, it may burn so hot that nutrients are vaporized and become airborne; shrubs that once provided erosion control and wildlife habitat may be eradicated; healthy trees may not survive. This speaks to the importance of prescribed fire in these communities where the specific set of variables such as temperature, humidity, and time of year may be accounted for. Prescribed fire enables the flame size to be manageable and provide the goal of enhancing ecological benefits. 

References:

Florida Natural Areas Inventory

PDF

Florida Department of Agriculture and Consumer Services

The Natural Role of Fire