Comparing site productivity of mature fire-origin and post-harvest juvenile lodgepole pine stands in Alberta

Abstract

Twenty-two paired-plot sample locations were revisited to re-examine the site indices of mature fire-origin and adjacent post-harvest juvenile lodgepole pine (Pinus contorta var. latifolia Engelm.) stands occurring on the same physiographic sites. The post-harvest juvenile stands followed harvesting and drag scarification, whereas the mature fire-origin stands received no stand treatment. Results showed that the site index of post-harvest juvenile stands was 27% to 35% higher than that of the mature fire-origin stands. Calculation of the rate of change in site index indicated that the site index estimates of post-harvest stands were stable after 5 years breast height age was reached. This suggests that the increase in site index in post-harvest stands is not a short-term artifact, but a sustained gain that will be maintained over time. Simulations of post-harvest yield based on the Alberta growth and yield projection system (GYPSY) for lodgepole pine suggested that the increase in post-harvest site index will likely result in substantial gains in the mean annual increment and total yield of post-harvest lodgepole pine stands in the study area. The results of this study indicate that post-harvest lodgepole pine stands are growing significantly faster than their fire-origin counterparts on equivalent sites.