The productivity of Douglas fir in Ireland

A study was undertaken to quantify the yield class of Douglas fir on a sample of sites on which it has been planted and to model the relationship between the site factors and yield class recorded. In total, 117 stands of Douglas fir were surveyed and a variety of site factors were recorded. The yield class of the stands ranged from 8 m(3) ha(-1) a(-1) to 22 m(3) ha(-1) a(-1). Using regression analysis, a predictive model for yield class was developed, which included soil parent material, aspect and wind exposure. The precision of the estimates provided by this model ranged from +/-1.0 m(3) ha(-1) a(-1) to +/-6.4 m(3) ha(-1) a(-1).