Dendrochonological patterns of white spruce in the Noatak National Preserve in northwestern Alaska

Arbaugh, Michael; Suarez, Frank; Binkley, Dan

Historical growth patterns were studied at 10 treeline sites in the Noatak National Preserve in Alaska to examine the role of geography and topography on climate response. Six sites were located along the Agashashok River (80 km north of Kotzebue) and 4 sites were located along the Kugururok River (200 km northeast of Kotzebue). Three sites were on terrace areas of sediment deposited by historical flood events: three sites were located on hillsides adjacent to the river; and four sites were located at the forest-tundra ecotone on hillsides adjacent to the river valleys. Principal component analysis indicated that plots within drainages were similar, and that terrace sites differed from hillside sites. Climate information from the seven nearest weather stations was used to examine the patterns of monthly and seasonal climate variations as a function of residual ring-width for each of the sites. Ring-width correlations with multiple station averages were more consistent across sites than correlations using individual weather station records. Ring-width correlated positively with June temperature and negatively with previous July temperature for all sites. Each drainage showed characteristic climate correlations. The Agashashok sites correlated positively with November temperature and February precipitation, while Kugururok sites were positively correlated with September precipitation. There were also differences in climate correlations for the terrace sites relative to other sites within each drainage. These results indicate that geographical and topographical characteristics may influence tree response to climate at the northern tree line. It is also possible that the precipitation response observed, and some temperature responses, may indirectly influence growth through modifications of soil conditions.