Rock Cities - Part II

Yesterday we looked at how bedrock cliffs and float blocks form rock cities. Rock cities provide different habitats than the surrounding forest and are utilized by a variety of plants and animals. Certain plants, such as the small fern known as mountain spleenwort (Asplenium montanum), pictured above, are found almost entirely restricted to taking root in crevices in sandstone outcrops. Various species of lichens, liverworts and mosses also favor areas of less competition on bare outcrop surfaces, or beneath overhangs where there is more moisture.

Certain animals find important habitat at rock cities and cliffs. If the top of the outcrop is open and sunny, snakes, including pregnant timber rattlesnakes, gather for thermo-regulation (warmth) and protection. Where slabs of rock have moved to create dark protective “fracture caves”, or if large crevices exist, both turkey vultures (Cathartes aura) and the threatened Allegheny woodrat (Neotoma magister) are known to nest, and many other mammal species are known to den.

Perhaps one of the most adapted animals at southern Fayette County Pottsville outcrops is the threatened green salamander (Aneides aeneus), insert photo. With its compressed body structure and rock-clinging expanded toe tips, this species is able to inhabit tight fissures in the face of outcrops and float blocks. Its lichen-patterned green/black coloration provides camouflage. Courtship, egg-laying, brooding and hibernation occur in the rock crevices. Because this rare species' entire existence is tied to its specialized adaptations for sandstone habitat, the protection of these places is critical to its survival. WPC biologists were responsible or understanding the distribution of this species in Pennsylvania.

Photo from WPC library.

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