Calcareous glade monitoring at Chickamauga and Chattanooga National Military Park: Final report—third sampling of baseline transects established in 1993, 2023 revision

Govus, Thomas; Moore, Bill

doi:10.36967/2297338

Calcareous glades, sometimes referred to as cedar glades, are characterized by limestone and dolomite outcrops having very thin rocky soils and with extreme environmental conditions. These rare habitats are unique, highly specialized communities that support many rare endemic or near endemic species in the southeastern United States. In 1993, The Nature Conservancy established several baseline and monitoring transects within a subset of glades on Chickamauga and Chattanooga National Military Park for the purpose of tracking changes in these biologically significant habitats through time. Woody cover data were resampled in nine glades during the 2006 field season and two glades during the 2008 field season. Plant density data were also resampled in five glades during the 2008 field season. All woody cover and plant density data collected during the combined 2006 and 2008 seasons were collected again most recently in 2019. The conclusion of the researchers following the 2006-2008 effort was that there was a decline in the natural integrity of the glade communities most notably reflected in an increase in woody cover and declining populations of several herbaceous species characteristic of glade communities. Results from the 2019 effort suggest a continued decline. Specifically, Eastern red cedar (Juniperus virginiana) has exhibited a consistent increase in cover through time across a majority of the monitored glades. Between 1993 and 2019 this species has exhibited statistically significant, double digit increases in percent cover in eight of the 11 monitored glades. Though not nearly as dramatic as the increases observed by red cedar an additional 11 woody species have also exhibited statistically significant increases in percent woody cover in one or more monitored glades. As a result, a fundamental feature of the glades (i.e., their openness) is being lost, making it more difficult to distinguish the glades from the forest/woodland complex surrounding them. Additionally, glade endemic or near endemic species have shown statistically significant declines from 1993 to 2019, while others went undetected in some glades in 2019. Nashville breadroot (Pediomelum subacaule) and Gattinger's prairie-clover (Dalea gattingeri) exhibited consistent (and statistically significant) declines in the majority of glades where they were monitored. In most cases 2019 observed densities were less than half the densities observed in 1993 for these species. Other glade endemic or near endemic species, glade larkspur (Delphinium carolinianum ssp calciphilum) and Tennessee gladecress (Leavenworthia exigua var. exigua) had extremely low densities or went undetected in 2019 surveys. Exotics are also a concern. Chinese privet (Ligustrum sinense) increased substantially in glades 8A and 24A, and three glades (8A, 11, and 24A) now have total woody cover values at or near 10%. Chinese privet appears to be the only invasive species that poses a serious threat to the habitat integrity at the moment, but a new non-native species, waxy-leaf privet (Ligustrum quihoui) was detected on one transect in glade 6. To our knowledge, this occurrence represents a state record for Georgia and is of concern because it has been reported to be invasive in diabase glade communities in North Carolina. The removal of privet from the center and edges of these glades remains an important management priority.We are also supportive of the park’s plans to conduct a prescribed fire in the Viniard-Alexander Prescribed Burn Unit, which will impact glades 13, 14 and 24A, as well as other smaller glades and glade-like habitats in the vicinity. While it is hoped that fire will impact the encroachment of woody vegetation it is questionable whether fire alone will be enough to restore the previously open nature to these glades. If this proves to be the case, removal of individual red cedars should also be considered. This management action has been implemented successfully on other national park units as part of their glade management and restoration activities.

Calcareous glade monitoring at Chickamauga and Chattanooga National Military Park: Final report—third sampling of baseline transects established in 1993, 2023 revision

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