DENDROCHRONOLOGY REVEALS RESPONSE OF COASTAL PINE TREES TO VARIOUS CLIMATE PARAMETERS IN GRAND BAY NATIONAL ESTUARINE RESEARCH RESERVE, MISSISSIPPI, U.S.A

Climatically sensitive trees grow in regions where trees experience stress related to water availability and temperature limitations, yet the climate sensitivity of trees growing nearest to the ocean where saltwater is present has yet to be explored. We hypothesize that trees growing on the margin of freshwater-brackish environment are sensitive to climate variability similar to those in arid regions or those growing near temperature-limiting tree lines. Our study site is located in the Grand Bay National Estuarine Research Reserve Mississippi (GBNERR, 30°40’N, 88°41’W) where we sampled 30 Pinus elliottii var. elliottii (slash pine) on a tidally-influenced island adjacent to periodically flooded salt marshes located ~1.5 km from an open saltwater bay. Standard methods are used to develop earlywood (ERW), latewood (LRW), and total width (TRW) tree-ring chronologies spanning 1909–2014 for comparison to climate indices. We find significant correlations between average May–October Standardized Precipitation-Evapotranspiration Index (SPEI) and TRW (r=0.4, p<0.05), average March–May SPEI and ERW (r=0.4, p<0.05), and average July–October SPEI and LRW (r=0.5, p<0.05) reflecting direct influence of SPEI on P. elliottii growing seasons for this location. Additionally, we find El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are significantly correlated to TRW for March–July (r=0.4, p<0.05), whereas the Atlantic Multidecadal Oscillation (AMO) is not, suggesting this coastal site is under the influence of Pacific climate variability whereas locations further inland are sensitive to the AMO. These results suggest that subannual growth of maritime slash pine at GBNERR is partially limited by coastal processes (i.e., brackish groundwater, aerosolized salt), which makes individuals sensitive to climate variability. More specifically, drought conditions negatively affect growth for each respective growing season and climate variability (ENSO and PDO) likely drive weather patterns that are important to the radial growth of near shore P. elliottii trees. This work lays the foundation for additional research with older trees in similar environments that can be used as proxies for water resources and climate variability in the United States Coastal Plain and similar coastal regions.