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Managing Granite Outcrops with Fire: A Meeting with Malcolm Hodges, Retired TNC Director of Stewards

by Daniel Crescenzo

Dan and Malcolm met at Camp Meeting Rock Preserve to discuss fire on granite outcrops. Photo by Malcolm Hodges

As Stewardship Director, I am responsible for ensuring that the conservation easements Oconee River Land Trust holds are being followed. This means preventing soil and vegetation-disturbing activities inside riparian buffers and special natural areas, including granite outcrop habitats. I’ve known for a while the importance of fire for encouraging species diversity in upland forests in the Georgia Piedmont, but I only recently considered: Should granite outcrop habitats be burned so that they remain healthy and retain their species diversity?

This question let me to insightful conversations with Buck Marchinton of DNR’s Wildlife Resources Division, U.S. Fish and Wildlife Service Biologist Mincy Moffett, Jr., Eric Brown, the Nature Conservancy’s Stewardship and Fire Manager, and Malcolm Hodges, retired Director of Stewardship for the conservancy. These conversations culminated in a meeting with Malcolm at the Nature Conservancy’s Camp Meeting Rock Preserve.

As Malcolm and I toured the preserve, with its large granite outcrop and rich assortment of habitats and species, I got to see firsthand how decisions about how to use fire around outcrops were guided by natural history – where fires would have been historically likely to start, and their historical frequency, for instance – and the need to preserve species and habitat diversity.

I learned that fires should be started in neighboring forests every 2 – 3 years and then allowed to burn toward the outcrop, but should never be started on an outcrop, in outcrop edge habitat, or in a vegetation island surrounded by exposed granite. This is because even small amounts of fuel are poisonous to the biofilm (algae and lichens) on the outcrop, and historically, fires would have more often started off of the outcrop and seldom reached vegetation islands.

Lichens and moss growing on ephemeral flow over an outcrop. Photo by Dan Crescenzo

Fires should also be set under the right soil moisture and weather conditions and drop fires should be utilized as needed to moderate intensity of fire as it approaches the outcrop. Drop fires are small fires started in the path of the main advancing fire in order to reduce fuel load for the main fire before it arrives. While the fire gives grasses, herbaceous species, and fire-resistant woody species a competitive advantage over species that aren’t fire-adapted and encourages species diversity, it is important to keep fire intensity lower in the outcrop edge habitats to avoid damaging these species . This approach also makes plowed firebreaks, which are disruptive to fragile plant communities around granite outcrops, unnecessary.

By burning the oak-hickory-pine and pine-dominated forests around the outcrop, and allowing the fires to burn up to the outcrop edge, fire tolerant species of grasses and wildflowers are able to thrive. By not burning the island of vegetation in the middle of the outcrop, fire intolerant species such as Eastern red cedar, pawpaw, and witch hazel are able to thrive. And by not starting fires on the outcrop itself, the biofilm on the exposed rock is able to remain healthy and rare species in the vernal pools, such as snorkelwort (Gratiola amphiantha) and black-spored quillwort (Isoetes melanospora), are able to flourish. The result is that each assemblage of diverse species has a place to grow, and the overall habitat and species diversity and resilience of ecosystems on the land is preserved.

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