CLIFF-EDGE HEMLOCKS (TSUGA CANADENSIS) IN THE NORTHWESTERN ADIRONDACKS: SENSITIVE INDICATORS FOR PALAEOCLIMATE RECONSTRUCTIONS?

The northwestern Adirondack region is a large, rural and sparsely populated area of northern New York; as a result, there is a paucity of climate and palaeoclimate data for reconstruction work. In an effort to support future palaeoclimate work in the region we have begun testing the sensitivity of commonly occurring hemlocks (Tsuga canadensis). In order to maximize climate sensitivity, we collected data from 30 hemlock trees growing at or on a 3-10 meter, gneissic cliff edge in South Russell, NY. Processing our tree-ring data using both COFECHA and ARSTAN resulted in a master chronology dating from 1900-2014 (correlation coefficient of 0.585). Of important note is the mean sensitivity, or measurement of year-to-year variability in tree-ring width, of the chronology at 0.292. Based on the COFECHA analysis of every published hemlock chronology in the International Tree-Ring Database from Ontario, Quebec, Maine, New Hampshire, Pennsylvania and New York (650-kilometer radius), our sensitivity value is the 2^nd highest recorded in this area (n=38, mean=0.234, std=0.028). With this high mean sensitivity, we processed the ARSTAN master chronology using DendroClim 2002 for climate controls on growth and temporal stability. Results suggests that these sensitive hemlocks are responding positively (i.e., increased ring width/growth) in association with warmer November and Decembers (growth year -1) and warmer Aprils (growth year). Results also reveal that warmer Julys result in decreased growth the following year; no association with precipitation was revealed. Spectral analysis, via the MTM cohere program, revealed both 5 and 7 year cycles driving growth (at ~95% confidence); possibly, El Nino Southern Oscillation events(?). Although this chronology is a mere 114 years in length, improved selection of old-growth hemlocks in similar conditions will likely provide a deeper understanding to centennial-scale climate variability in this relatively empty region of the Adirondacks.