SREL Reprint #3543

Belowground carbohydrate reserves of mature southern pines reflect seedling strategy to evolutionary history of disturbance

Joshua T. Mims1, Joseph J. O’Brien2, and Doug P. Aubrey3,4

1Department of Biology, Georgia Southern University, Statesboro, GA 30460, USA
2USDA Forest Service, Southern Research Station, Athens, GA 30602, USA
3Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA
4Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA

Abstract: Carbohydrate reserves provide advantages for mature trees experiencing frequent disturbances; however, it is unclear if selective pressures operate on this characteristic at the seedling or mature life history stage. We hypothesized that natural selection has favored carbohydrate reserves in species that have an evolutionary history of frequent disturbance and tested this using three southern pine species that have evolved across a continuum of fire frequencies. Longleaf pine (Pinus palustris) roots exhibited higher maximum starch concentrations than slash (P. elliottii) and loblolly (P. taeda), which were similar. Longleaf also relied on starch reserves in roots more than slash or loblolly, depleting 64, 41, and 23 mg g-1 of starch, respectively, between seasonal maximum and minimum, which represented 52%, 45%, and 26% of reserves, respectively. Starch reserves in stems did not differ among species or exhibit temporal dynamics. Our results suggest that an evolutionary history of disturbance partly explains patterns of carbohydrate reserves observed in southern pines. However, similarities between slash and loblolly indicate that carbohydrate reserves do not strictly follow the continuum of disturbance frequencies among southern pine, but rather reflect the different seedling strategies exhibited by longleaf compared to those shared by slash and loblolly. We propose that the increased carbohydrate reserves in mature longleaf may simply be a relic of selective pressures imposed at the juvenile stage that are maintained through development, thus allowing mature trees to be more resilient and to recover from chronic disturbances such as frequent fire.

Keywords: fire; non-structural carbohydrates; roots; starch; stored carbon

SREL Reprint #3543

Mims, J. T., J. J. O'Brien, and D. P. Aubrey. 2018. Belowground carbohydrate reserves of mature southern pines reflect seedling strategy to evolutionary history of disturbance. Forests 9(10): 653.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).