Restoring natural characteristics in managed Norway spruce [Picea abies (L.) Karst.] stands with partial cutting, dead wood creation and fire: immediate treatment effects

Abstract

This study investigated the immediate effects of restorative treatments on stand structure in mature managed Picea abies-dominated stands in southern Finland. The restorative treatments consisted of partial cuttings with three levels of coarse woody debris (CWD; 5, 30 and 60 m3 ha−1) with a constant volume of standing retention trees (50 m3 ha−1), and a burn/non-burn treatment. In addition, burned and unburned reference stands without cutting treatment were assessed. Each stand (n=24) included an upland and a paludified biotope; the paludified biotopes burned only partially. Detailed descriptions of stand structure were made for living and dead tree components before and after restorative treatments. Changes in tree diameter distribution and increases in standing dead tree volume were greatest in the combined burning and cutting treatments. The resulting standing dead wood volume varied greatly (1–52 m3 ha−1) between treatments, and was highest on burned paludified biotopes with 60 m3 ha−1 of CWD. The results indicate that creation of down wood was needed to achieve burning and that it is possible to regulate the severity of burnings through the amount of CWD, according to ecological restoration objectives. The study demonstrates that living and dead tree structural characteristics typical of natural postdisturbance early-successional forests can be rapidly restored to mature managed spruce stands, even when a significant portion of wood volume is harvested. These types of restorative cuttings provide one potential means of conserving biodiversity in managed forests.