Utilizing Cellular Level Radial-Growth Anomalies as a Paleoclimate Indicator

Intra-annual density fluctuations (IADF) are cellular-level radial-growth anomalies in trees where earlywood-(latewood-) like cells are present within the latewood(earlywood) of annual growth rings. Previous investigations, which have principally focused on Pinus species in the Mediterranean region have identified four IADF classification types with two each occurring in earlywood and latewood. IADFs are triggered by climate anomalies (e.g., late-spring frost, early-season drought) and the synchronistic occurrence of IADFs across a chronology suggest that the cellular location IADFs can be utilized for paleoclimate reconstructions (e.g., identification of a growing-season frost event). Considerably less work on IADFs has occurred in North America and no published studies have examined southeastern U.S. pine species. In this work, we analyze IADF and missing-ring occurrence in 120 longleaf pine (Pinus palustris Mill.) cores collected from four sites in western Florida, USA. The study region is affected by several climatic anomalies including winters with minimal days (i.e., ≤ 2) below subfreezing conditions and the influence of tropical cyclone-induced heavy rainfall events (i.e. >25 cm/event). Here, we identify the temporal occurrence of IADFs during 1950-2017 and determine if they are congruent with climatic anomalies and synchronized across the chronology. We then determine if evaluation of IADFs for longleaf pine is an operative means to examine intraseasonal climatic anomalies prior to the historical climate record.