EVALUATING CLIMATE EFFECTS ON TREE RING WIDTHS IN THE CHAMPLAIN VALLEY, NEW YORK

Two populations of red pine (Pinus resinosa) from the Champlain Valley were analyzed to consider the effects of climate and microclimate on ring widths. Cores were collected using standard increment borers from 21 trees on Willsboro Point (WP) and 23 trees on top of Rattlesnake Mountain (RM), both near the town of Willsboro, NY. The RM trees grow at an elevation of 343 - 384 m while the WP trees are at an elevation of 35 m, 6 km to the northeast and directly above the 29 m shoreline of Lake Champlain. Although these stands are close to each other and grow on thin soil, they are expected to have different microclimates due to the differences in elevation and proximity to Lake Champlain.

Cores were crossdated visually and then statistically checked in the program COFECHA. The program ARSTAN was used to detrend the raw data using a spline with a 50% frequency cutoff of 32 years and to combine cores into ring width chronologies. The WP chronology has 41 cores and spans 187 years while the RM chronology has 33 cores and spans 142 years. Both chronologies have negative correlations with average summer temperatures in NY climate region 7 (Champlain Valley). The WP chronology also has strong positive correlations with monthly Palmer Drought Severity Index values for region 7.

Microclimate effects were investigated by comparing the two chronologies using a 15-year running correlation. The data strongly correlate through the majority of their overlap with four exceptions; the 1890s, the 1920s, the 1960s, and after 1998. The weak correlations in the 1920s, 1960s, and after 1998 may be explained by known events; the development of property on WP in the 1920s, clearing of the canopy and trees after a large fire on RM in 1957, and the ice storm of January 1998. The exact reason for the weak correlation in the 1890s is uncertain, although it may be a result of logging on RM. In all but the current period of low correlation the trends of high and low growth rates for each series generally match. This indicates that ring widths from these two populations are primarily responding to the same climatic forcings. After 1998, the RM ring growth is much smaller than in the WP trees. This may be a direct difference due to a microclimate effect; the RM area was heavily hit by the ice storm while the WP stand was spared by the warmer lake temperature, receiving only rain.