Height growth and competitive relationship between paper birch and Douglas-fir in coast and interior of British Columbia

We examined height growth patterns of paper birch and Douglas-fir in two different biogeoclimatic zones (the Coast Western Hemlock and the Interior Cedar and Hemlock) in British Columbia. Stem analysis data from 20 paper birch and 20 Douglas-fir showed that height of Douglas-fir exceeded height of paper birch at about 50 years after stand establishment at the interior site. In comparison, Douglas-fir exceeded paper birch in height at about 25 years at the coastal site. Difference in height growth patterns of the two species at the two sites contributed to the explanation of differences in the distribution and persistence of paper birch between these two biogeoclimatic zones. This means that the interspecies competitive relationships are different in the two biogeoclimatic zones. However, other differences between the two different biogeoclimatic zones, such as differences in growing degree day, length of growing season, frequencies of natural fire, insect outbreak and forest diseases, may also be important in determining why paper birch is more abundant in the Interior Cedar-Hemlock zone but not in the Coastal Western Hemlock zone. (C) 2002 Elsevier Science B.V. All rights reserved.