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Future climate change is expected to have many impacts on forest ecosystems. It is important to have some understanding of these impacts in order to make informed forest management decisions. A major consideration in making forest management decisions is the productivity of a site, as measured by site index. In this study, I relate Douglas-fir site index to accumulated growing degree-days greater than 5°C (DD5), as well as to soil moisture and nutrient regime. This allows the impact of climate change on forest productivity to be estimated. A two step approach was followed. The first step derived models to estimate various climate variables to latitude, longitude, and elevation using data from climate stations. Then, these climate variables were used along with soil moisture and nutrient data to predict site index for the site index plots. A two step approach was taken because climatic data were not available for the site index plots. The trend was for site index to increase with both increasing soil moisture and nutrients, although the site index decreased on the wetter sites. Site index also increased with DD5 at the rate of 1.2 m for every increase of 100 units in DD5. These models can be used together to evaluate the impact of various climate change scenarios on site index. [ABSTRACT FROM AUTHOR]

The best estimates of site index, an indicator of site productivity,are obtained from site trees. Undamaged site trees should be sampledto obtain unbiased estimates of site index. Two juvenile height growth modelling projects provided us with sufficient data to assess our ability to select undamaged lodgepole pine (Pinus contorta var. latifolia Dougl.) and white spruce (Picea glauca (Moench) Voss) site trees. The sample trees were split open to measure height growth from the terminal bud scars. Splitting the stems also revealed damage that wasnot visible from the outside of the tree. Over 50% of the lodgepole pine trees and 75% of the white spruce trees had damage, which was much higher than expected. Possible causes of damage are frost and insects. The damage does not significantly reduce the height of the spruce trees, but there is evidence that the heights of the lodgepole pinetrees are reduced. [ABSTRACT FROM AUTHOR]