João Campôa;Joshua J. Puhlic

CENSE – Center for Environmental and Sustainability Research, CHANGE - Global Change and Sustainability Institute, Department of Environmental Sciences and Engineering, NOVA School of Science and Technology, NOVA University Lisbon, Campus de Caparica, 2829-516 Caparica, Portugal;The Jones Center at Ichauway, 3988 Jones Center Drive, 39870, Newton, GA, US

Longleaf pine;Slash pine;Pinus elliottii;Climate change;Dendrochronology;Dendroclimatolog

The longleaf pine (Pinus palustris Mill.) ecosystem is an endangered ecosystem in the southeastern USA, and efforts to restore the species are ongoing. However, in recent decades, the region has experienced drastic fluctuations between wet and dry growing season conditions from year to year, and it is not fully understood how these fluctuations have influenced the growth of P. palustris. To address this topic, we cored P. palustris trees in woodlands of southwest Georgia and used dendrochronology techniques to determine how climate fluctuations have influenced the growth and drought resilience of P. palustris. We also cored slash pine (Pinus elliottii Engelm.) trees in the same woodlands to compare growth between species. While P. palustris growth was less impacted by adverse climate conditions compared to P. elliottii, the strength of correlations between P. palustris growth and temperature, precipitation, and Palmer Drought Severity Index (PDSI) changed over time. In recent decades, climate conditions during the growing season became more influential on P. palustris growth than the previous year's conditions. This is concerning given that drought severity during the growing season has been increasing. Our results also indicate that P. palustris was less resilient to droughts during the 2000s and 2010s than to those of the 1950s. Under this new climate paradigm, our results suggest that P. palustris might be more susceptible to growth reductions and less resistant to droughts than once expected. This work highlights the importance of understanding the impact of novel climate conditions on P. palustris and has implications for restoration efforts, such as using silvicultural treatments that reduce tree vulnerability to drought (e.g., thinning) and promote other climate-adapted species in mixture with P. palustris.