A Method for Measuring Sub-Annual Ring Widths of Pinus Edulis for Seasonal Climate Reconstructions

Abstract

Pinus edulis is one of the most ubiquitous tree species in the US Southwest. It accounts for over a fifth of the total number of trees in New Mexico alone. Its prevalence and relatively long-lived nature makes it an ideal candidate for dendroclimatological studies of the North American Monsoon. The problem occurs with delineating the boundary of the earlywood and latewood for sub-annual reconstructions. In this study, we present a novel method ("the resin duct method") for delineating the latewood boundary using resin ducts of P. edulis from three sites in New Mexico. The climate sensitivity of partial ring widths of P. edulis is then explored and compared to co-occurring Pinus ponderosa, which has a clear latewood boundary. The method of using resin ducts for delineating latewood in P. edulis resulted in a statistically significant relationship when compared to the latewood widths of co-occurring P. ponderosa. Although we found a similar climate response of P. edulis when compared to P. ponderosa, P. edulis latewood was a poor predictor of North American Monsoon precipitation unlike P. ponderosa. However, P. edulis earlywood has a statistically significant correlation with cool-season precipitation, making it useful for cool-season climate reconstructions in the Southwest. © 2017 by The Tree-Ring Society.