Oklahoma Natural Heritage Inventory
Oklahoma Natural Heritage Inventory

Devil's Den, Johnston County

Granite outcrops dominate the landscape of Devil's Den Natural Area along Pennington Creek in south central Oklahoma. Several different plant communities are associated with granite rock outcrops.  One unique plant community can be found in depressions on the surface of granite hills.  Soil accumulates in these shallow basins on the rock surface and creates an "island" of plants on a bare stone "sea." 

The plants that grow in these islands must tolerate the physical conditions of high temperature, low moisture, and high sun exposure.  Many plants are short-lived and quickly grow and reproduce during a favorable time of year.  Their seeds can tolerate the difficult environmental conditions and will be ready to germinate when the conditions are more suitable.  Instead of escaping the adverse living conditions, some plants cope with a series of morphological adaptations.  For example, cacti found in these depressions conserves water by having spiny leaves that reduce evaporative surface and protect from herbivores.  The spiny leaves also shade the body of the plant and reduce the surface temperature during the grueling Oklahoma summer afternoons.  These islands host a diverse and unique plant community; over 40 species of plants can only be found in granite rock depressions!
Devil's Den is also host to a rare, riparian shrub. In Oklahoma, the Seaside Alder (Alnus maratima) is only found along a few creeks and rivers in Johnston and Pontotoc counties. Scientists are particularly interested in this plant because the only other places it grows is the coast of Maryland and Delaware and in Georgia (and no where in between!). This disjunct range continues to puzzle botanists and biogeographers.

Seaside alder has cone-like flowers and fruits.

(photo copyright 1997-2005 David G. Smith, www.delawarewildfowers.org)

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