Vol. 4 | No. 4 | June 2011
A third native forest community to consider — shortleaf pine/oak/hickory with its native groundcover
By Dr. Kevin Robertson, Fire Ecology Scientist
Traditionally in the Red Hills region of northern Florida and southern Georgia, frequently burned and thinned pine forests and their groundcover of herbs and shrubs have been categorized as longleaf pine/wiregrass (native) or loblolly/shortleaf pine old-field (post-agriculture) communities. However, certain forests in the region are dominated by shortleaf pine and have no wiregrass, yet they contain many plant species that usually do not become re-established in old-field forests (goat’s rue, bracken fern, running oak, twin-flower, and several others). These forests are similar to native forests in the Piedmont region and in parts of Louisiana, Texas, Arkansas, and Oklahoma.
We hypothesized that this third community type represents a native community type referred to in other regions as shortleaf pine-oak-hickory. We compared groundcover plant species composition in 100 square meter plots, tree species composition in 20 meter radius circular plots (1256 m2), and soil characteristics at more than 20 locations in each of the three community types on Tall Timbers Research Station (Florida) and Pebble Hill Plantation (Georgia). Multivariate analysis ((NMS), see scatter plot graph below) showed the three community types to be distinct in their species composition.
Results from Nonmetric multidimensional scaling (NMS) multivariate analysis of 100 m2 plots. Proximity of symbols indicates similarity in species composition and color represents community type, where green is longleaf pine-wiregrass, blue is shortleaf pine-oak-hickory, and red is old-field pine.
Of the total 225 plant species identified, indicator species analysis identified 54 species significantly associated with longleaf pine-wiregrass, 15 species associated with shortleaf pine-oak-hickory, and 25 species associated with old-field community types. Longleaf pine-wiregrass and shortleaf pine-oak-hickory communities showed greater depth of the topsoil than old-field communities, suggesting less of the erosion typically associated with old-field communities. Shortleaf pine-oak-hickory forests also had the highest concentrations of calcium, potassium, magnesium, and manganese of the three community types, which may partly explain the difference in species. These results are consistent with our hypothesis, suggesting that native shortleaf pine/oak/hickory forests should be recognized according to their indicator species and protected from further soil disturbance and conversion to other land uses.