Microsites before and after restoration in managed Picea abies stands in southern Finland: Effects of fire and partial cutting with dead wood creation

Abstract

Different types of microsites, e.g. CWD (coarse woody debris), mounds, and uprooting pits, are important for tree regeneration and biodiversity. However, microsite diversity is greatly reduced in managed stands. We studied how restoration treatments changed microsite distribution in mature managed Picea abies stands. Four cutting treatments were used: uncut, low-CWD (5 m3 ha-1 of down retention trees, DRT, and 50 m3 ha -1 of standing retention trees), intermediate-CWD (as previous but leaving 30 m3 ha-1 of DRT), and high-CWD (as previous but with 60 m3 ha-1 of DRT). Timber harvested from stands ranged from 108-168 m3 ha-1. Half of the stands were burned, and half remained unburned. Sampling was stratified into upland and paludified biotopes within each stand. The pre-treatment microsite distributions were dominated by level ground in both biotopes; mounds and microsites on or next to CWD or a stump were slightly more abundant in the paludified than in the upland biotopes. Microsites were more diverse after cutting, with and without fire. The cutting treatment increased the relative abundances of microsites on or next to CWD. Fire consumed small diameter dead wood and flattened mounds. Microsites were more diverse in paludified than in upland biotopes. The results demonstrate that microsite diversity can rapidly be restored to structurally impoverished managed Picea stands despite a large portion of wood volume being harvested.