Spontaneous development of early successional vegetation improves Norway spruce forest soil after clear-cutting and renewal failure: a case study at a sandy-soil site

Abstract

Clear-cutting is the most common silvicultural system. Sometimes, if the new crop is not established successfully, clearcut is left unreforested. This study focused on a site where early successional species such as silver birch (Bi) and rowan (Ro) were accompanied with Norway spruce (Sp) in 13-year-old stand from natural regeneration at 550 m of altitude at an acidic site with eastern aspect and 25% slope. We found five types of stand composition: treeless gaps, Ro-Bi, Ro-Bi-Sp, Bi-Sp and monospecific Sp. Besides these juvenile ones, adjacent 100-year-old spruce (Sp old) stand representing pre-harvesting conditions was studied. In addition to the performance of trees, organic layer (Hum), topsoil (Ah) and upper subsoil (B) horizons were sampled to study an expected shift of chemical properties after clear-cutting and secondary succession at the site of interest. Birch dominated the natural regeneration; rowan and spruce were present mostly in understorey. Old spruce was more acidic and nutrient-poorer compared to the juvenile treatments. The treeless treatment showed also slightly higher pH and comparable nutrients compared to the young mixtures. Young spruce was higher in nitrogen compared to Ro-Bi-Sp mixture.