Leaf area index and productivity in eastern Washington forests

Abstract

The relationship between Leaf Area Index (LAI) and current stem-wood production was examined in selected stands in eastern Washington. Stands were sampled with an angle gauge (prism). LAI was estimated from sapwood area; current stem-wood production from DBH, height, and radial increment. Maximum LAI attainable on a given site has been related to qualities of the environment. Where stocking varies on a given site, LAI is related to the degree of utilization of the available resources. The average leaf area per tree, relative to average tree size, is a measure of stand vigor. To compare the relative sapwood area of trees of different sizes, allometric regressions of sapwood area from DBH were derived, for five species, from fully stocked stands. In fully stocked stands with dominant Douglas-fir, current productivity was more closely related to average LAI than to either Site Index alone or predictions by Cochran (1979) based on Site Index, basal area, and age. Within stands displaying a range of stocking on a given site, wood production per unit of leaf area decreased as LAI increased; nonetheless, productivity per hectare generally increased up to the highest LAI observed in each stand. Both the pattern and the scale of the relationship between LAI and productivity differed among sites.