Influence of climate on the growth of quaking aspen (Populus tremuloides) in Colorado and southern Wyoming

Abstract

We analyzed a series of increment cores collected from 260 adult dominant or co-dominant quaking aspen (Populus tremuloides Michx.) trees from national forests across Colorado and southern Wyoming in 2009 and 2010. Half of the cores were collected from trees in stands with a high amount of crown dieback, and half were from lightly damaged stands. We define the level of stand damage based on stand survey data in which lightly damaged stands had average crown dieback of 16% and heavily damaged stands averaged 41%. Upon analysis, two-thirds of the cores collected did not exhibit radial growth correlated with region-wide patterns (e.g., climate) and were classified as having a low cohesive response. The site variable most predictive of whether a stand exhibited high cohesive response or low cohesive response was site elevation, followed by aspect, slope, and canopy closure. Sites with high cohesive response stands were more likely to have aspen bark beetle damage, white rot, and Cryptosphaeria canker. We did not detect relationships between tree growth and summer precipitation from 1900–2008, but there was a relationship between growth and annual precipitation. A growth model included maximum May and July temperatures, as well as the current and previous year’s annual precipitation.