Native upland pine savanna communities once dominated the southeastern U.S. Coastal Plain, but most have been converted to other land uses, including row-crop agriculture, where there is complete loss of native flora and fauna and severe soil disturbance. Restoration of pine savannas on post-agricultural land through frequent fire and ecological timber management has progressed over the past century. Previous studies have shown that many native plant species recolonize such areas and that they provide habitat for many animal species of special concern. However, such studies typically compare native and restored communities at a single point in time and do not consider the successional processes that would allow prediction of the potential for native community restoration through succession. We present a chronosequences approach to infer long-term changes in plant community composition and structure, bee species composition, soil microbial communities, and soil physical and chemical characteristics over approximately one century following abandonment of agriculture and restoration of frequent fire and open-canopy pine forest. We measured species composition and environmental variables to compare row-crop agriculture, post-agricultural pine savannas with varying amounts of time since abandonment, and native pine communities to infer the potential for full restoration of native communities.
Results/Conclusions
Restored plant communities showed increasing similarity toward the native community with increasing species richness and grass coverage, and a reduction of exotic species over time. However, native communities remained fairly distinct from even the most mature restored pine savannas because of a suite of plants that do not become re-established. Soil characteristics showed much more rapid progression toward native conditions, including decreases in bulk density, pH, phosphorus, calcium, magnesium, and potassium, and an increase in carbon. The soil microbial community showed a similar trend and was indistinguishable from the native community after 50 years. The bee community in row-crop agriculture differed from pine savannas as a whole, (restored and native), but a trend towards native savanna was not evident. There appears to be great capacity for agricultural fields to be restored to functional pine savanna over 100 years and provide many valuable ecosystem services including high biodiversity of native plants, habitat for rare species and pollinators, carbon sequestration, timber resources, and recreational hunting. However, full restoration of the native plant community was not achieved through this form of passive restoration of succession under natural fire regimes.