Effect of timing of precommercial thinning on the consumption of working time in Picea abies stands in Finland

The effect of the timing of precommercial thinning on the productivity of work was examined in young Norway spruce [ Picea abies ( L.) Karst.] stands in southern Finland. The common problem of large variation between sample plots in time studies was avoided by introducing a new approach based on a combination of stand measurements, tree-ring analysis and existing work productivity functions. The results indicated that a 2 year delay in the precommercial thinning of a stand was enough to cause an increase of 10 - 42% in the consumption of working time at a mean height of 1.5 - 3.1 m. At a later thinning, at a mean height 4.1 - 7.2 m, the increase was 8 - 24%. The development of the stand up to the first commercial thinning was not significantly influenced by a 2 year delay in the late precommercial thinning.