Reconstruction of Seasonal Precipitation in Louisiana Through the Analysis of High-Resolution Intra-Ring Stable Carbon Isotope Signals of a Longleaf Pine (Pinus palustris) Tree

Abstract

Across many regions of the planet, observational data indicate global warming attributed to anthropogenic influences is driving changes in seasonal precipitation patterns. Many climate models, however, lack the ability to accurately predict regionally specific changes in precipitation at seasonal scales. Stable carbon isotope ratios within tree ring tissues have been used in numerous studies to reconstruct climate data at annual resolution, and high-resolution studies hold great promise in allowing for the development of regionally specific and seasonally resolved precipitation data. In this study, I determined 307 stable carbon isotope values across 23 annual growth rings of a longleaf pine tree to reconstruct a regionally specific and seasonally resolved precipitation record. The period of study (1990-2012 C.E.) covered a wide range of precipitation conditions (1 to 417 mm/month) experienced within a pine savannah ecosystem characterized by low-permeability soils. The goal of the study was to utilize the intra-ring δ¹³C data to test the effectiveness of a global relationship between δ¹³C values and seasonal precipitation for a site with fine-grained, poorly drained soils, subject to highly variable precipitation lacking in distinct seasonality. The results showed significant correlation (Summer: r = 0.76; Winter: r = 0.62) between instrument-measured and isotope-derived seasonal precipitation values. This study adds to the growing worldwide archive of tree-ring isotope datasets and demonstrates that the proxy relationship between seasonal variations in δ¹³C values and seasonal precipitation can be applied with confidence to sites with low-permeable soil and highly variable precipitation lacking in distinct seasonality.