COS 180-5 - CANCELLED - A loblolly pine for tomorrow: when genetics, physiology and modeling collide for more resilient forests

Abstract: Climate change is leading to more frequent and extreme hotter-drought events globally, which have been associated with growth declines and increasing mortality risk across Earth’s forests. Yet, the climate-resilience for both growth and survival of many tree species remains largely unknown. Thus, our overall goal is to understand the diversity of physiological trait combinations that can confer climate resilient growth and survival. Specifically, to determine genetically-based growth and survival trait combinations that confer climate resilience in loblolly pine (Pinus taeda L.), an ecologically and commercially important tree species, and to discover ideal and possible trait combinations to improve species growth and survival on our warming planet.

We are sampling a common garden of loblolly pine, located in Gainesville, FL, containing replicated SNP-genotyped clones from 315 provenances representing the entire species range. Each genotype is sampled for the characterization of climate-resilient growth traits such as turgor loss point (TLP), maximum photosynthesis rate (A_max), and the optimal temperature for carbon assimilation and water use efficiency (A_opt and WUE_opt­, respectively). Thermal limits and dehydration-tolerance curves are also being established to determine critical temperature (T_crit) and relative water content (RWC_crit) values at which cellular death occurs. Combining the climate-resilient traits determined for each genotype and using the SurEau model, an ideotype is generated to represent an elite breeding line of tree.

Our existing results encompassing the broad distribution of loblolly pine (sampling provenances from Virginia, Georgia, Florida, Alabama, and Texas) reveals high variability in the traits evaluated. Depending on the provenance, TLP varies from -1.43MPa to -2.25MPa; A_max from 3.51 µmol.m^-2.s^-1 to 6.94 µmol.m^-2.s^-1, A_opt from 27.57°C to 35.07°C, and WUE_opt from 22.58°C to 32.56°C. Although those differences arose, traits were present in different combinations across genotypes and no genotype presented the ideal combination of traits making it most climate-ready. However, simulations conducted based on these measurements predicted a modeled ideotype outperforming provenance averages by extending the potential time for growth (by up to +40%) and survival (+68%) during hotter-drought stress. Thus, identifying ideal traits combinations within loblolly pines can inform present-day deployment, and future breeding efforts, to improve the climate resilience of this economically important timber species. In addition, conducting such studies on additional forest species can inform forest conservation and management decisions. Thus, identifying and planting climate resilient species, provenances, or cultivars could strengthen the climate resilience of forests, hence reducing the risk of further dieback in the face of global warming.