A half-century of harvest, site preparation, and reforestation practices result in successful regeneration in Interior Alaska boreal forest. Miho Morimoto, University of Alaska, Alaska, USA.

Additional Authors: Glenn P. Juday, Brian D. Young

Adequate tree regeneration is a crucial factor for sustainable forest management. In Alaska, sustainable yield standards for tree regeneration have been established in the Alaska Forest Resources and Practices Act (FRPA). In addition to the legal mandate, an increased demand for woody biomass to meet energy demands requires a more comprehensive understanding of post-harvest regeneration because of a potential for shorter rotations. However, long-term regeneration post-harvest has not been previously thoroughly evaluated. This study evaluates harvest and post-harvest treatments for sustainable yield in the Fairbanks area of the Tanana Valley State Forest within Interior Alaska by: (1) testing if harvest units continue to be adequately stocked under FRPA regulations, up to 40 years post-harvest, (2) testing whether there are significant differences in regeneration among different harvest method, and (3) examining how much woody biomass has accumulated over the 40 year time span post-harvest. To address these questions, we sampled 699 subplots (1.69 m radius circular plot) from 27 harvest units. The harvest units were selected to represent the diversity of types of harvest (clearcut or partial cut), site preparation (scarified or unscarified), and reforestation (naturally regenerated or planted white spruce seedlings), year of harvest (1975-2004), size of harvest area, and geographical location. We compared stem density, quadratic mean diameter, mean height, basal area, and biomass of trees and tall shrubs among types of harvest, site preparation, and reforestation. Regeneration post-harvest was successful in all units based on the Alaska state standards. Larger trees and greater density of trees tended to occur in scarified units, suggesting that site preparation is effective in promoting tree regeneration. Within planted harvest units, planted white spruce seedlings were larger than naturally regenerated white spruce. However, naturally regenerated white spruce seedlings were significantly smaller in planted than in naturally regenerated units. This indicates that planted seedlings suppressed growth of naturally regenerated white spruce seedlings. Moreover, biomass accumulation of white spruce was lower than broadleaf species, suggesting that it might be better to use broadleaves for biomass harvest. These findings will assist forest managers in addressing various management goals. If the goal is to produce more biomass, site preparation by itself could be adequate; however, if the goal is to produce larger dimension wood products in the shortest time, planting white spruce seedlings is likely to be more successful.