Seminar Abstract

Dave Peterson

Thursday, May 13, 2004
1:30 to 3:00

Spatial and temporal variability in tree growth-climate relationships in the Olympic Mountains, Washington

Spatial and temporal variability in tree growth-climate relationships is largely unknown for many Pacific Northwest forests, yet it is this information that is needed to predict how forests will respond to future climatic change. We studied the effects of climatic variability on tree growth at 71 sites in the western and northeastern Olympic Mountains. Basal area increment time series were developed for each site, and Pearson correlation analysis and factor analysis were used to quantify growth-climate relationships.

Tree growth in the Olympic Mountains responds to climatic variability differently as a function of mean climate and elevation. Low summer moisture limits growth across all elevations in the dry northeastern Olympics. Growth at low elevations in the wet western Olympics is associated with phases of the PDO and with summer temperature. Heavy winter snowpack limits growth at high elevations in the western Olympics. In the warmer and wetter greenhouse climate predicted for the Olympic Mountains, productivity at high elevations of the western Olympics will likely increase, whereas productivity at high elevations in the northeastern region and potentially in low elevations of the western region will likely decrease. This information can be used to develop adaptive management strategies to prepare for the effects of future climate on these forests.

This study shows that growth-climate relationships on the Olympic Peninsula vary at small spatial scales. Modeling at smaller spatial scales is needed to provide more accurate predictions at local to regional scales.