ORIGINS OF THE FLORA

The Ketona Glades and their environs provide suitable habitat for more than 60 vascular or nonvascular plant taxa of conservation concern. This is an extraordinary number for a habitat that totals roughly only 100 hectares, marking these areas as one of the most significant reservoirs of botanical diversity in the eastern United States. While all of the factors responsible for the development of the unique Ketona Glade ecosystem may never be fully understood, especially the full phylogenetic histories of the strict endemics, enough is known to suggest some hypotheses.

It seems certain that edaphic factors, especially soil chemistry, have played a major role in the development of the characteristic Ketona Glade communities. In addition to the four samples of topsoil indicated previously as having been submitted to the state Soil Testing Laboratory of Georgia, we gathered samples from several other rock outcrop communities and submitted them also, for comparison. The results are summarized in Table 3. When compared to other outcrop soils, that of Ketona Glades is seen to be extremely high in the element magnesium. The Ketona Formation is, as stated earlier, an exceptionally pure dolomite, comparatively free of the usual siliceous impurities that serve to dilute the levels of magnesium and calcium in a mineral otherwise composed almost entirely of CaCO₃ and MgCO₃, in a ratio of about 55:45 (Rheams 1992).

Of the soils sampled, only those derived from serpentine and diabase have comparable levels of magnesium. They differ critically in being acidic, while those formed from Ketona Dolomite have a mildly alkaline pH. The former also differ in containing much lower levels of calcium and much higher levels of heavy metals. Outcrop soils that have a pH greater than 7, in common with Ketona Dolomite soil, have lower levels of magnesium. In short, the Ketona Glades have a distinctive soil chemistry, in particular a combination of very high magnesium levels and mildly basic soil reaction. In addition, the shallowness of soil and high insolation values make the glades drought-prone in the extreme. The peculiar soil chemistry and low organic matter content of the Ketona Glades, in combination with extremely low soil moisture levels in summer, provide conditions that are hostile to ordinarily adapted plants. Such a habitat strongly selects for specialized adaptations, promoting endemism or, at the very least, ecotypic differentiation. And because the Ketona Formation is restricted to central Alabama, and outcrops of other rocks as high in magnesium, such as serpentine, are unknown in Alabama, at least as pavements (Adams et al. 1926), this community is isolated both geographically and edaphically. Our choice of the term "Ketona Glades" to refer to these places is due to our conviction that the chemical composition of the bedrock is chiefly responsible for the unusual plant assemblage.

Earlier, under "Biological Communities," we listed a number of characteristic plants of limestone glades that are absent or essentially so from the Ketona Glades. Some of these taxa may be unable to tolerate the presumably higher summer temperatures of glades at the latitude of Bibb County, while the propagules of others may simply have failed to reach the Ketona Glades. However, the distributions of several characteristic species of limestone glades (e.g., Heliotropium tenellum, Hypericum sphaerocarpum, Ratibida pinnata, and Verbena simplex) appear to skip over the Ketona Glades only to recur south of them, on chalk glades of the Black Belt region. This lends support to the theory that the absence of some limestone glade taxa from the Ketona Glades may be due to an inability to thrive in soil with such a high concentration of magnesium.

It is conceivable that some of the Ketona Glade endemics, such as the new Dalea or Liatris, may once have been more widespread, with a refugium in that portion of the Ridge and Valley that would likely have experienced the mildest climate during the Pleistocene. If so, it would seem that they were unable to compete within the new communities that developed over most of their former range as the climate subsequently moderated, and thus were unable to reclaim their former territory. Some elements of the flora seem clearly to represent relictual biota, such as Paronychia virginica, Silene regia, and Solanum pumilum, while others, such as Astrolepis integerrima and possibly Liatris cylindracea, appear to represent long-distance immigration.

Perhaps Ketona Glade communities once occurred outside of Bibb County, or possibly still exist and remain to be discovered. The Ketona Formation is not restricted to Bibb County, but is mapped (Szabo et al. 1988) as extending into Blount, Chilton, Shelby and, most extensively of all, Jefferson County. The formation takes its name from a place in the latter county, and Ketona is home to several quarries in the formation. The exceptional purity of the formation has made it valuable as a "flux" stone in the steelmaking process (Rheams 1992), and its abundance, combined with ready access to water and to deposits of iron ore and coal, is responsible for making Birmingham, the county seat of Jefferson County, a major steelmaking center. Our efforts to find any glades within the extensive areas mapped in Jefferson County as Ketona Dolomite were, with one exception,⁽¹⁰⁾ unsuccessful, for much of the area has been quarried, and most of the rest is occupied by commercial or residential development. Their comparative remoteness from Birmingham is probably all that has saved the Bibb County glades from a similar fate.

In summary, the existence of the extraordinary assemblage of plant taxa on the Ketona Glades of Bibb County, Alabama is best explained as resulting from a combination of strong selection for edaphic specialization, geographic isolation, freedom for many millennia from drastic climate change (fostering relictualism), chance long-range dispersal events, and placement within a rural setting where human impacts to the landscape have been comparatively moderate.

CONSERVATION STATUS

Over the several years since the discovery of the Ketona Glades, The Nature Conservancy of Alabama, U.S. Alliance Coosa Pines Corporation, and the Bibb County Commission have worked together  cooperatively to permanently protect about 120 hectares of glades and surrounding hardwood and longleaf pine forest. Currently, many of the largest and highest quality glades are protected within the Conservancy's Bibb County Glades Preserve. The preserve also protects more than a mile of riverine and riparian habitat along the Little Cahaba River, which harbors many imperiled and narrowly distributed aquatic species, including rare snails, mussels, fishes, caddisflies and the spectacular shoals spider lily, Hymenocallis coronaria (Chris Oberholster, The Nature Conservancy of Alabama, pers. comm. 2000).

CATALOG OF VASCULAR FLORA OF KETONA GLADES AND THEIR ENVIRONS

The following is an annotated list of taxa that we recorded from one or more Ketona Glades or their immediate vicinity. Except where indicated, nomenclature is that accepted at the time of writing by the PLANTS Database (USDA 2000). The names of taxa designated (at the time of writing or at any time during the study) to be of conservation concern by the Alabama Natural Heritage Program are preceded by an asterisk (*); names of taxa considered to be exogenous additions to the flora are indicated by a plus sign (+). For the most part, only uncommon or phytogeographically noteworthy taxa were recorded from surrounding areas, beyond glade-forest ecotones; these names are placed within curved brackets, { }. Synonyms that have been used in recent decades are provided within square brackets, [ ]. Finally, for those taxa of which we made specimens, we append the collection number of a voucher deposited (except where a different acronym is provided) at the herbarium of the University of Alabama (UNA).

PTERIDOPHYTES

ASPLENIACEAE

Asplenium platyneuron (L.) B.S.P.

Asplenium resiliens Kunze

DENNSTAEDTIACEAE

Pteridium aquilinum (L.) Kuhn

ISOËTACEAE

*Isoëtes butleri Engelm., A. and S. 7552

OPHIOGLOSSACEAE

*Ophioglossum engelmannii Prantl, A. and S. 7646

POLYPODIACEAE

Pleopeltis polypodioides (L.) Andrews & Windham var. michauxiana (Weatherby) Andrews & Windham [Polypodium polypodioides (L.) Watt var. michauxianum Weatherby]

PTERIDACEAE

{Adiantum capillus-veneris L.}

*Astrolepis integerrima (Hook.) Benham & Windham [Notholaena integerrima (Hook.) Hevly, Cheilanthes integerrima (Hook.) Mickel], A. 6695

*Cheilanthes alabamensis (Buckl.) Kunze, A. 12574

Cheilanthes lanosa (Michx.) D. C. Eat.

Pellaea atropurpurea (L.) Link

GYMNOSPERMS

CUPRESSACEAE

Juniperus virginiana L. var. virginiana

PINACEAE

Pinus echinata P. Mill.

Pinus palustris P. Mill.

Pinus taeda L.

ANGIOSPERMS

ACANTHACEAE

Ruellia humilis Nutt., A. and S. 7787

Ruellia strepens L.

ACERACEAE

Acer leucoderme Small

AGAVACEAE

Manfreda virginica (L.) Salisb. ex Rose [Agave virginica L., Polianthes virginica (L.) Shinners]

Yucca filamentosa L.

ANACARDIACEAE

Rhus aromatica Ait.

Rhus copallinum L.

Rhus glabra L.

Toxicodendron pubescens P. Mill. [T. toxicarium Gillis, Rhus toxicodendron L.]

Toxicodendron radicans (L.) Kuntze [Rhus radicans L.]

APIACEAE

{Eryngium integrifolium Walt.} (single locality), A. and S. 8112

Eryngium yuccifolium Michx. var. yuccifolium

Thaspium barbinode (Michx.) Nutt. var. chapmanii Coult. & Rose (variety not accepted in PLANTS [USDA 2000]), A. and S. 7558

Thaspium trifoliatum (L.) Gray var. aureum (L.) Britt.

Zizia aptera (Gray) Fern.

APOCYNACEAE

Amsonia ciliata Walt. var. tenuifolia (Raf.) Woods. [A. ciliata Walt. var. filifolia Woods.], A. 10566

Amsonia tabernaemontana Walt.

Apocynum cannabinum L.

AQUIFOLIACEAE

{Ilex ambigua (Michx.) Torr.}

ARALIACEAE

*{Panax quinquefolius L.}

ARECACEAE

*{Rhapidophyllum hystrix (Pursh) H. Wendl. & Drude ex Drude}, J. Allison and C. Oberholster 7057 (VDB)

Sabal minor (Jacq.) Pers.

ASCLEPIADACEAE

Asclepias tuberosa L.

{Asclepias variegata L.}

Asclepias verticillata L.

Asclepias viridiflora Raf.

Asclepias viridis Walt.

Matelea gonocarpos (Walt.) Shinners, A. 10898